tangles. are you seeing artifacts and texture corruption on the screen.
Both are a sideaffect of overclocking but more often than not HEAT.
The soprano case while it does have a few fans and looks nice, it does not cool down your pc too well, I had the Tsunami case which is like the soprano but all aluminum, and I thought that the side casefan was positioned VERY POORLY for my 7950GX2 1gb card which is 2 7900's sandwhiched together on a single PCI slot.
I had some similar issues with that case, if i played for more than an hour i would experience random crashed, BSODs, and random resets. very annoying.
I took the side fan off and pointed a fan on a stand into it and it was more stable but still it wasnt quite a long-term soution..
In the end, I bought one of these and it fixed all my issues.:
And its the most free flowing and best case I have ever purchased.
I think its rated as the case that pretty much is the pinnacle of air cooling atm, no other pushed as much air as this.
its ~200dollars tho. so there might be other things you can try to see what the problem may be first.