Blackberry 9360 Random reboot/rest

Hello..
I have a Blackberry Curve 9360.. Recently I've been having this problem, My blackberry keeps rebooting by itself at random times for no reason and no apps running except bbm, especially when I talk on the phone.
I tried reloading the software.. didn't work. Tried wiping it with JL_Cmder and didn't work.
Its band free. and I don't think its overheating :S
Does anyone has the solution of this annoying problem?

you need to replace your battery.

And why is that??
Why wouldn't RIM include it in the warranty?

i was having same problem with my 9360 and i replaced it with my coworker and every thing was fine, my battery worked with his phone and his battery worked with my phone and no more random reboots for me.