2 minutes past midnight

Recently in the study ...
 
Long session, starting just after lunch ... tracking lead vocals, followed by the usual editing, a rough mix, then throw away some of the crap, re-record, fix, then ad libs ... Sonar working fine, despite vocals being tracked against a fairly plugin-heavy sub mix ...
 
2 minutes past midnight, during recording of some final ad libs, the odd audio drop-out game starts; hiking up audio buffers doesn't fix it, neither does re-syncing clocks, or even restarting Sonar ... it's late; time to call it quits; time for beer ... no worries about the project as the last backup is 10 min old ...
 
Next morning, no changes to the system, just a cold boot ... everything works fine at same settings. no further issues, neither when tracking nor mixing ... 
 
no clue what caused that forced break; i can't really be Sonar or the project, as it worked fine again. some driver? maybe. probably not an update service, either; these are all disabled ... the world of win7 remains mysterious ...
 
 

No anti-virus installed. The DAW is not on the net. Files to be transferred to the DAW are scanned prior to loading on a different PC ...

it could be your computer telling you its time for a beer  :)
but seriously, im with these guys, looks like it could be a task running in the backseat.
either/or have you cleaned out temp files lately ?
sometimes a cold boot will wipe out anything that's being saved in random memory, so hence the re0boot, you start with a fresh slate.
im not sure if this would make a huge difference but have you made modifications to your picture cache in sonar ?
maybe its overflowing and needed a reset ?

that last one was just reaching but as well something to sleep on.

Look in Windows Control Panel - Administrative Tools - Task Scheduler. On the left, use the expanders to open up Task Scheduler Library - Microsoft - Windows. Windows will open up to a bunch of applications. On my machine there's an entry for DiskDiagnostic - in the center lower pane there are a set of tabs, including 'Trigger'. My machine shows that this diagnostic triggers every Sunday every two weeks at 1:00 AM. Other entries also show their start times, typically late at night, sometimes every night. You could try changing the Trigger time on some of these, or disabling at least temporarily, to see if that fixes it.

UltimateMusicSnob


Look in Windows Control Panel - Administrative Tools - Task Scheduler. On the left, use the expanders to open up Task Scheduler Library - Microsoft - Windows. Windows will open up to a bunch of applications. On my machine there's an entry for DiskDiagnostic - in the center lower pane there are a set of tabs, including 'Trigger'. My machine shows that this diagnostic triggers every Sunday every two weeks at 1:00 AM. Other entries also show their start times, typically late at night, sometimes every night. You could try changing the Trigger time on some of these, or disabling at least temporarily, to see if that fixes it.

Thanks for that. I had thought that I had eliminated these scheduled tasks, but didn't realize that there are still some many "hidden" ones that you only find if you go looking in the right place. I was quite shocked to see all the rubbish that's to executed once it's past midnight ... all this customer experience crap and some more useless tasks ...
 
So I deactivated most of the remaining and postponed what seems relevant to 5 in the morning ...
 
 

Yeah, this is how Microsoft makes "user-friendly" computing - by choosing to do it for us, and then burying the controls deeply enough that people won't ever see them in the first place. Glad to help, hope it solves your problem. Guess you'll have to wait for midnight Sunday to find out...

...or just do a CTL+ALT+DEL and open the task manager and look at the services tab...see what's running, and if you're really saavy, look at the running processes...

More than likely, your Windows Task Scheduler has a scheduled event with Trigger=Midnight and Action=Beer_For_Bertl

Sounds like a plan - just don't get mixed up and cool your CPU with cold beer.