thomson android mid1002

i have just recently got a thomson tablet for christmas after having it all set up it worked great for a couple of days when i turned it on a couple of days ago it booted up great until i got to the lock screen the a message saying android is upgrading starting apps came up when the slide screen appeared again after 2 seconds it jumped back to the android word logo and has been doing that for three days now. every now and then it will bring up an error message saying "unfortunately the process.com.android.phone has stopped working"how do i fix this please help.