You can try to do a hard reset to restore it back to factory settings.
All your contacts, messages, calls, applications, themes > everything will be gone. So BEWARE. Backup your important stuff first. Your memory card will be fine, so anything there will be saved. However, if you have applications installed on the memory card, I recommend deleted those as well.
Your phone will run faster, as will the applications. Leave the memory card for your media.
Anyways, to perform a hard reset on the Nokia N82 you do this.
Type *#7370# from the standby screen while your phone is one
It will ask for the lock code which is 12345 unless you have previously changed it. Make sure you do this right, because if you do it too many times the wrong way you can lock up your phone.
Also....
Hard/Soft Reset phone!!!???
*#7780# - Reset to the original settings; some informations are also deleted and need to be re-entered.
*#7370# - Soft format - this will resets all the phone memory (like re-format a disk); make sure to have full battery charged !
[Green]+[def3]+[*+] during a power on performs a hard format : this will return the phone like you have received; make sure to have full battery charged !yeah, and you need to keep the pwr button held too... not just press it to turn on and then only hold the other 3 buttons.
if above option dosent solve then there may be display chip/LCD/Flex ribon problem,Consult a local mobile expert for help !