This one is a real mystery to me... it's happened quite a few times, but it's not something I can "create" the scenario to occur... I'll be working on a mix and during replay, there will be a patch of white noise suddenly appear in the mix... When it occurs, it will always be at the same point in playback, (even if you start the playback from another location). Example: The white noise will appear on track 3, at the beginning of measure 55. If you solo track 3, you'll hear the noise at measure 55. If you mute track three the noise goes away. If you start playing at measure 1, the white noise will be at measure 55.. if you start playing at measure 50, it will still be at measure 55... If you listen to the underlying audio files in the Audio folder, these noises will NOT be there. If you don't save, but quit and reload the project without restarting the computer... the noise will still be there at the same location... If you quit, restart the computer, the noise will be gone... unless you foolishly SAVED the project... in which case the noise is yours to keep... At first I thought I'd been overpowering by using too many plugins... But tonight it happened before I'd inserted a single plugin. It doesn't happen often, but when it does, it pretty much screws up my workflow, and by the time I get back into the project, my mind's not in the groove of the song, it's pissed off because of the white noise problem. By the way... this has happened to me both on my Compaq Presario Desktop PC, AND on my HP Laptop. Makes me wonder if I should upgrade to X2 when it comes out or look elsewhere... Any ideas?

Do you have Amplitube in the project on a guitar?  You mentioned track 3... is it the guitar? 

Since Amplitube is a plug in the underlying waves will NOT have the noise burst in them. It is added by the plug in while it is reproducing the effected audio in playback.

Amplitube does this until you register it properly.  Although it comes with Cake products, it is registered through a different server.... not a cake server. 

Once registered, that noise will go away. It's a protection scheme to keep unauthorized users from using it.

Yea, its most likely not sonar and most likely a plugin that needs to be registered.

Cj

I had this occur once and it was recently. It was on a tom track. The waveform in this area looked nothing like a typical waveform. When zoomed in, there were lines of varying length hanging down from the top of the track and lines of varying length sticking up from the bottom. Fortunately it was in a section with no tom hits and I was able to delete it that section. And when it occurred, it was quite loud. Mine was definately digital white noise.
 
Mine had absolutely nothing to do with an unregistered plug. I was running a fully registered instance of Amplitube on a different track, certainly not a tom track.
 
Have used every upgrade from CWP8 thru 8.5.3 extensively and as I said, it's only happened that one time and was in 8.5.3.

It's not amplitude, even if it was, my copies of X-Gear and Amp3 are registered and activated. I just tend not to use them. This last time, though, I can guarantee that it wasn't a plugin because... I hadn't put any in yet. I was still doing my gain staging, all I had done is move faders. I can't see any extra info in the waveform when you zoom in on it. Even after I saved the project, the underlying waveform in the Audio Directory was fine. I'd only mentioned the guitar track and measure as an example. It's happened several times on several projects, and the tracks that pick up the noise seem to be random, and once they've picked up the noise, playback in Sonar will ALWAYS have them in that project... but if you don't save after it introduces the noise, just exit, restart the computer, and reload the project, the sound is gone... If you just exit the project and come back in (even though you didn't save) the sound comes right back.

Makes me wonder if I should upgrade to X2 when it comes out or look elsewhere... Any ideas?

X2 is not going to fix this problem. This is not a Sonar problem. You have either a demo plug-in or some other issue. I'll give it some thought, but I'm fairly certain the upgrade isn't going to fix it.  No one else has reported this sort of problem so this has to be specific to something you have or have done. 

It sounds like you've recorded the noise onto the track. Do you see the noise in the waveform? 
You might try disconnecting all inputs and then replugging them in one at a time to try to isolate where its coming from.  
Maybe you have a bad cable from your guitar. Check your cables out. 

Any  layers active on the noisy track? Something not currently visible in track view?

If there are layers, I'd be shocked. The last time it happened (yesterday) the following things had been done: A) All tracks were imported one at a time from the raw stems. B) All volume faders had been lowered 10db (without automation on, just lowered the faders). That's it. No plugins, not even the Sonitus:FX EQs in the channels were turned on.

that happened to me every time I recorded a new song, seems like - the weird noises.  I got rid of them by switching to strictly instrumental music.  I think singing lessons might have worked, too, but that took too long....

3rd song in a row this is happening... I HAVEN'T PUT ANY PLUGINS YET! First as I import the files... random noise in some track... delete track, reimport, gone... Then I change a fader.. .random noise appears IN A TRACK I DID'NT EVEN TOUCH... delete track, reimport, gone. I'm fighting a losing battle, and looking at Studio1 and Protools websites...