I'm having the same problem with heat... My pc is getting a bit too hot..
We both got Prescotts (yours is a Prescott build, right?)... They get a bit hotter then the Northwood cpu's..
You processor can be 75 ~ 80 degrees celcius, without problems...
If you hit 120 degrees celcius, i'll be dangerous because the core melts (well, at boilingpoint maybe even more than just the core.... cables etc)
You can try upgrading your cooler.. I guess you're using a "stock" fan, Intel delivered on your CPU... There are a lot of good fans, you might want to try a Zallman cooler, they are very good and not too expensive...
Try searching Google on some reviews, most of them are positive..
Second, airflow is important.. Cables can block it, and multiple fans can also...
You're videocard is a High end one, which get pretty hot aswell.. You can also put a new cooler on it (the only problem is that your warranty is voided sometimes, but well...)
On the freezing specific... I've heard that it sometimes helps when you
disable HyperThreading.... I haven't tried it though as i'm still waiting for my disk to be delivered
Good luck, and if you've got any questions about what i've said you can send me a PM!