Hi,
I'm experiencing an issue with my Fireface UC. Everything works perfectly for 20-30 minutes, when for no apparent reason sound gets distorted as if sample rate was improperly set.

When this happens all sounds produced by OSX get distorted as well. Issue disappears by:
- closing and restarting the application in use
OR
- setting sample rate to a different value and resetting it back to 44.100 kHz (if Logic is the application in use, sample rate is restored automatically to 44.100 kHz as soon as I try to change it, and sound gets properly restored)

System: iMac12,2 (Mid-2011), "Core i7" 3.4 GHz processor
OSX:10.7.3, 10.7.2
Application involved: Logic 9.1.6. Same behaviour happens with any other application (e.g. VLC, iTunes...)
Driver version: tried both newer driver versions and latest classic totalmix version

Sometimes (not always) upon distortion I get a "ClipIfNecessary()" error in Kernel.log.

Apart from this issue, fireface is working properly for both recording and mixing event at lower latencies. In fact issue is not related to latency in any way (I get the issue for 32, 64, 128, 256 and 512 as a latency value). Issue happens systematically (if I let a movie play for 30 minutes or so I always experience this issue).
Using the fireface UC from Windows (xp and/or 7) everything works great. I even tried connecting to an older MacBook model (Snow Leopard 10.6.6) and got no issues at all. Re-installing OSX from scratch did not fix the issue.

Can you please help me troubleshoot the problem?