I use my Saffire at 64-128 buffer often with GR5. The only thing that comes to mind is that "too low" can be CPU intensive, and GR5 has a built-in HI/LO CPU option in the upper right. Is that set to low?

I've found a few "solutions" that work:
(1) Running through the standalone version of Guitar Rig5 to hear what I'm playing, recording the output into the Sonar track (Thanks FreeFlyBertl)
(2) Turning Input Echo ON, Turning off FX globally in the menu bar, then turning Fx back ON with GR5 in the recording track.  Turning PDC off did not work.  (But thanks for the leading thought Deon_C.  And this thread on Input Echo delay: http://forum.cakewalk.com/FindPost/2746051.)
 
I'd like to understand the "why".  Maybe I'm dense, but should Input Echo introduce that much delay?  It's totally unusable without solution 2.  As noted above, I have very little latency in the system, and it's fine with other solutions, just not with Input Echo on.  I've had the same problem trying to give a little reverb while recording vocals.  So only an issue when I want to hear what is being recording with any kind of effect, and try to use Input Echo - it goes from no audible delay to what sounds like a 250ms delay for that track only.  And on this particular project, at this point in tracking I have essentially NO other effects on - just an acoustic guitar with no Fx and a vocal track with all Fx already turned off.

I run with an ASIO Buffer Size of 128 when recording, and do so with Input Echo On all the time, with no latency problems, so I am quite confused.
 
If you are running Windows 7, you can run either DPC Latency Checker or LatencyMon, and if you are running Windows 8 you can run LatencyMon.  Both are freeware programs.  You would download and run while Sonar is not running, for a 2-3 minutes, and then look at their analysis in the output, to get a feel for whether or not there is something outside of Sonar that is interfering with your DPC latency.
 
Oh, I am also running x64, with a Sample Rate of 48 k.
 
Do you happen to have WiFi?
 
Lastly, it sure sounds like something like an effect - something like a convoluted reverb, or Boost11 or that sort of thing.  Someone above this had asked about what happens if you bypass effects ('E' on your keyboard), but don't recall if you had posted back on that having any effect on things or not.
 
I have to run - but will come back and read through the thread again when I get back.
 
Bob Bone
 

Further to what Has been said, i had/still have latency spikes caused by my network driver. Wifi and Bluetooth are totally disabled.

On also disabling the network device driver in Device Manager (as against simply unplugging the network cable) the latency problem goes away completely.

Cheers,
Jerry

I'm not sure it's actually a computer "latency" issue(?), as it ONLY is an issue with Input Echo on, regardless of Fx setting.  (I didn't use keyboard "E", but used the FX button in the menu bar - pretty sure that's the same thing.)  It's fine running through standalone GR5 - It seems to me if if's processing latency of the computer alone, that should induce the same latency; but I get the delay with Input Echo on regardless of FX settings for that track or all tracks.  So I think you're right, there's something else inducing the processing delay within Sonar, since global FX off minimizes the delay.  But shouldn't turning off all Fx in every Fx bin do the same thing as global FX bypass?
 
This project is also sampled at 48k
 
And yes I have WiFi.
 
Also got rid of land line very recently and had a cellular module installed so our house phones run through a cellular "line", with the module being on the wall outside my studio.

MorganT
 So I think you're right, there's something else inducing the processing delay within Sonar, since global FX off minimizes the delay.  But shouldn't turning off all Fx in every Fx bin do the same thing as global FX bypass?
 

Do you have anything in the ProChannel that may cause latency in the processing??? Because that would explain a difference between turning off all Fx in every Fx bin vs. the same thing as global FX bypass ...
 
Also, double check that you don't have any active FX on buses which you may have overlooked ... or in hidden tracks ... or are you playing against a VSTs that'S not frozen???

I can run GR5 in Sonar with input echo enabled and no noticeable latency at all (24bit/44.1KHz, 48 sample buffer = 5ms round trip latency). I also input echo up to another dozen audio tracks at the same time, though once in a while I have to increase the buffer to 64 samples if I've multiple fx running as well.

Any latency you're getting isn't an inherent design problem in Sonar or we'd all be seeing the same thing.

Try going into Windows control panel/device manager. Right click on the wifi adaptor entry and disable (not uninstall) it before running Sonar. See if that makes a difference. Wifi adaptors are notorious for causing huge (in computer terms) latency spikes on data transfer through the PCI bus (which handles all the data flow through a PC) which aren't noticable for most PC uses but cause havoc with DAWs.

Secondly check you've no compressors using look- ahead or convolution reverbs in the project. They can also cause latency issues and are best added at the mixing stage. Some software synths can cause latency issues as well.

If I remember rightly, simply switching plugins to bypass does not have the same effect as bypassing all effects via the E hotkey or control bar. If a plugin is just bypassed in the channel strip or plugin interface Sonar treats it as if still operating because it can be switched on at any time (including by automation), so Sonar still makes allowance for the time the plug reports it needs to process audio. That way clicks, dropouts and lurches are avoided if the plugin is enabled while the transport is running.

The bypass all effects command should result in Sonar treating plugins as not existing at all.

Good input both; may be the ProChannels - I do have several modules in those.  Most are Sonar provided low-latency, but some are add-ins.  I didn't think about turning off Fx bins in channel strips not stopping the processing, good thought tlw, that makes sense.  At least a couple of explanations that may explain my issue. 
 
I misunderstood the WiFi question - I don't have a WiFi adapter on my music computer, just WiFi in my house.  This computer is hardwired to the network.  I double checked to be sure there wasn't a driver loaded and couldn't find one.

I would use external effects...stomp boxes, or all in one unit, or such...and record the guitar ...if you must have the effect on while recording...or get a uad with plugins of choice, or something a liken to add with out strain on cpu of the computer, or to reduce delay...if that works?...why not just clean guitar, and turn on the effects after the recording?...well I guess some play the effect..must be the reasoning here.?.

boss se70..got one for $50.00 last year, to add to the one I already have...does a lot,  two does more of...you can then use em linked in odd ways...first one takes in the guitar line splits to stereo outs ..take clean line out of effect box 1, to computer input and set to arm that track, the second line of box 1, run into the second unit input ,and add your flavor of effects, out to second line in of your computer input, arm second track...two tracks, one clean one dirty....and do the deed as need be with out any strain on cpu or using echo at all....total cost 150.00 bucks...and it does a lot for you in other terms as well....Not saying you need Boss se70 exclusively.(could be hard to find now?)..as many newer effects have multiple outs, and amps with effects and sends/returns these days exist... as someone suggested...think outside the box sometimes does help!...aux sends and a good mixing board also help ...get sorted before the computer and daw...to help the daw/computer work with out latency...