Myotuch 3g Random Reboots

I have a rooted Mytouch 3g. Running android 1.6(couldn't find the froyo update)and have titanium back up and link2sd installed(16gb sd card).
For some reason just recently my phone has been randomly rebooting(could be useing google maps, or just browsing the web using opera mini) and the phone will randomly reboot on me). Is there any type of tool that I can run on my phone or pc to find out what the cause is?. I installed rom manager a while back, but removed it since I couldn't get the S-off. When I reboot into recovery mode, it says E: can't open /cache/ recovery/comand
What does that mean?

By any chance, do anyone on here have the froyo update for a Mytouch 3g 32b? I want to try it on my phone and see if it fixs the reboot issue. i have tried google and have only found the part 1 file, part 2 file is gone and leads to a dead link.