Problems with SetCPU on Sidekick 4G
Absolutely yes. I have a SK4G as well, and tried SetCPU out too.  It force closed regularly; whether it's due to overheating I can't say for sure, but it seems the most likely cause.

FYI, all the SK4G ROMs are based on the stock ROM as no one's reverse-engineered the hardware requirements to build custom kernels for it yet :(