problem started when my iphone 3gs date & time resets every time battery drains out ( it was on IOS 4.2). then one time it turned itself off and Itunes screen "activation screen" came up with info sign instructing that (IMEI :0000 - ICCID:0000).
I thought its a software thing so updated it to IOS 5.01 and since then it wont activate and Itunes says " there's a problem with your iphone - could be damaged or service cant be activated.

Note: 1- it was unlocked before but i restored it earlier before & it was working fine for a year.
2- iphone keeps on restarting.

Is there anything i can do ?!