My wife's iphone 3g just froze at the lockscreen. The slide bar is unresponsive and there is nothing I can do to unlock it. Powering down and rebooting only gets it back to the frozen lockscreen. The phone is warm to touch and battery also seem to drain rapidly. Connecting it to iTunes, iTunes recognizes the phone, and proceeds to sync it. After a few minutes the phone reboots itself back to the lockscreen. I can scp into the phone, but am not sure how to remedy the situation.

Here are some details of phone: firmware 3.1.2 and modem 05.11.07

I have blobs saved for firmware 4.0 onwards, but unfortunately not for 3.1.2 or 3.1.3.

Any suggestion as to how to fix the problem?
Should I need to restore the phone, is there anyway that I can restore to a sub 4.0 firmware? Also, a step by step process to restore so that I do not upgrade the baseband would be appreciated.

Thanks much.

Just wanted to let you folks know that I successfully restored the phone to the 3.1.2 firmware. The following are what I did:

Downloaded a custom 3.1.2 firmware
Entered DFU
Shift-Entered and located downloaded firmware to restore
Placed original AT&T SIM for activation (Not sure if I really needed to)
Phone restored and successfully brought back contacts, messages etc.,
Upon restoration, went to jailbreakme.com and jailbroke.
Ultrasnow was already in the Source list in Cydia, just had to install it
Gave me miscellaneous errors that I had to manually 'fix' some files. A reboot fixed it, and I was able to install ultrasnow (unlocked)
Downloaded Aptbackup and restored to get back my Cydia downloads. (Only got back a few)

For some reason, (perhaps because it is a 3G), it did not matter that I did not have SHSH blobs saved for this particular firmware.

Hope that the above helps someone.