I also have been suffering through almost constant resets, crashes, etc for the past two weeks. If I factory reset the phone and don't sync to ANY email (google or activesync) then I have no problems. Sync to either, but especially activesync and it all falls apart. I also have it set for manual updates. I get crashing while reading email, when the phone rings, just in my pocket, etc. It doesn't run hot, and reboots just fine...
I have my third phone ready at the Sprint store to try out. Could an update to activesync have caused all of this?