Your K800 should still be under warranty, so the easiest way would be to bring it back to the place where you bought it.
Reflashing the firmware could help, but you can't be sure about that.
You can either buy an account to download the files here if you need them quickly or buy some logs for an overtheair flashing service like Wotanserver, D-Client, Kulankendi, SE King, etc...

Please read the tutorials carefully if you decide to flash the phone on your own. Don't forget to backup your GDFS.