Not at home at the moment so I can not check the driver versions I have but I've never seen this with either my Fireface UFX or Fireface 400.

Hi,
I have an RME UFX and used to get this exact message a while back with an older RME driver and Sonar X1.  In my situation, the symptom would occur in 3 situations:
1. When switching from one ASIO application to another.  For example, if I was using BFD2 or any other ASIO application in standalone mode, then closed that out and started up another ASIO application, such as Waves GTR in standaloe mode or Sonar.  It would occur whether the two apps had the same or different default sample rates configured.
2. When the sample rate of the project didn't match my default sample rates in Sonar.
3. When changing sample rates in a program or within a project within Sonar.
 
After speaking with both Cake and RME about the issue - they informed me it was the result of the driver not being 'released' properly when a program was closing (so another program opened afterward couldn't open the driver properly, as  in #1 above), or when sample rates were being reset (as experienced in #2 and 3 above). 
 
Assuming your sample rates are set the same in Sonar and the RME Driver interface sofware - it may be the RME driver issue.  If nobody else is having similar issues with the same version you're running, maybe try reinstalling it - or downgrading to a previous version.  I'm not home right now - so can't tell you what version I'm running - but I last upgraded my RME driver about 2-3 months ago and it's been running perfectly stable, so maybe just downgrading to the previous version will help you.  I shoudl also mention I'm currently running my UFX via USB2, but was running it via Firewire previously when experiencing the issue.  I don't believe I've ever experienced the issue when running via USB, but can't be sure, as it was a long time ago.  I switched to USB at RME's recommendation. 
 
Hope that helps.
Russ
 

I have the latest firmware and drivers for the UFX and got this msg 4 times yesterday..

...yeah I'm not sure what to do at this point.  I didn't have any problems with X1 although I was on Windows 7 then but I don't think Windows 8 is the problem.  Basically, similar setup just a faster CPU with more RAM - same TI chipped PCI Firewire card I've been using since I bought the FF800 and never had a single driver hiccup until now.
 
I thought about maybe going back to Win7 but I see someone else on the thread having the same problem but he's running on Win7.  I'm using X3d, the very latest RME driver (it was doing it already with the previous version which is what prompted me to go out and look for a newer driver and found the one from the last week in Feb).
 
I guess when I get a few minutes I'll try and call RME and see what they say.  I really don't want to switch to USB (not even sure I can with the FF800) - seems completely senseless to do something like that.  I'm at a loss - I'll try the allow/arm changes checkbox and see if that works...
 
I am not trying to switch between other apps/programs that use the ASIO interface.  Sonar is the only thing I'm using there so I can't see how that could be the issue either.
 
Pretty damn frustrating to be sitting on over $15k worth of hardware/software and have some weird anomoly issue like this popping up after running Sonar/RME for over 6 years on 3 different hardware platforms without a glitch.

I sent an email to RME but in the meantime here's what I've done.
 
Uninstalled/reinstalled RME latest driver for the FF800.
Enabled the "Allow Arm changes during recording/playback" in preferences
 
I checked device mangler and it shows my RME connected to the TI 1394 Chipset Device.
 
I checked the TI Chipset driver and it just shows the standard Windows Driver (never seen an update for this available as even an optional update on WU) from 6/21/2006.  Version is 6.3.9600.16384.  I tried using the 'update driver' from the device manager and letting is search WU and it came back with "you have the latest driver...".  So, not sure that there's anything new on that front.
 
My TI Firewire card is a PCI variant that I bought a few years back with my RME FF800 after doing the research.  I've been using it for years now and this is my 3rd PC/hardware upgrade and the first time I've had any problem like this.  Never can say it's definitely NOT something...but have a hard time believing it's the Firewire card...
 
I fired up X3d from a hard reboot and have a 30 second loop on a project I'm working on playing right now and going to see how long it stays up before it dies...if it does (fingers crossed).  Right now it's been going about 5 minutes without any problem so we'll see...
 
I'll update after I get to hammer on it more...

I posted this issue on the RME forum last night. Feel free to logon there and chime in. I seriously doubt that it is a firewire vs. USB issue since it happens on both types of protocols.

...yeah, didn't fix it.  :(
 
It died a while ago and then wouldn't start back up after clicking NO.  I got some RME message saying that the driver requires version 2.77 of the firmware to run.  Hmmm, I know I updated that.  I checked the RME driver in the tray and sure enough 2.77 was the firmware version.  But, I downloaded the firmware tool anyway and re-updated and started all over again.  The loop runs about 8 minutes or so and then I get the dreaded error message.
 
So #$%@#$ frustrating.
 
I was going to go contribute to your RME Forum post but I click on the FireWire forum and get this.  RME is on their game right now. :)

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fwiw - I used to have a FF800 w/FW and started getting these messages in the X series of SONAR. Never seen them in 8.5 or I don't remember seeing them.

Yeah I didn't do a X2 upgrade - went from X1 to X3 and I don't remember seeing these even in X1.  I certainly didn't see them in any 8.x release I used.
 
I'm at a loss...hopefully we hear something from RME on this.

OK, went through this myself a year ago. I tried everything. Finally I gave up and bought an Octacapture to replace it. THEN when I pulled out the firewire cable I heard something fall off inside the computer. When I looked inside, I noticed that the connector had fallen off of the Firewire board! All along, this was caused by a bad connection! There were two connectors on the back, so I used the other one and haven't had a problem since.