Pro Tools LE 8.0.5 - Noise and the playback stops when moving the mouse. Any ideas?

Hey guys, I've been using the Pro Tools LE 8.0.5 for about 3 years now without any major problems, unless the problem clearly was me (which it usually is).



Now for some reason(s) out of a blue, now whenever I move the mouse, I get clicks and crackles, the playback stops and I get the charming message





" The audio device buffer underflowed. If this occurs frequently, try decreasing the "H/W Buffer Size" in the Playback Engine panel or remove other devices from the audio firewire bus. (-6085)





The thing is, I haven't made any changes to my PC nor added any plugins etc to my PT setup, nothing at all. No problems with my PC either (OS Windows 7)



Any ideas what might be going wrong / whats going on?



By the way, I'm quite sure this is something that has been answered before, so my apologies for asking the same thing, I Did look for an answer to this one but did not find one.



I did pick up one advice which is setting the buffer size to 1024, thanks for the tip, that allows the playback to continue but the crackling is still there (and annoyingly so).





I wonder what the problem might be? Like I said, this really came right out of the blue. Never had this issue before.



I did change the USB cable as well (the only thing I could think of), no difference.





I hope you guys can help.



Thanks!