Question : Login procedure seems to crash

It seems after AVG has been updated along with several Microsoft updates there was a spyware item detected by AVG.  After removing the spyware I was unable to login again.  I get an error message saying something like group policy... login failure and media was protected.  The message comes and goes fast.  I've made several attempts to restore the computer to an earlier point and was able to do so once, but then after restarting logging in and updating microsoft (automatic) the system went back to the login crash as before.  

what can be done to correct this?

Answer : Login procedure seems to crash

Possibly one of the updates that you have installed is interfering with AVG definitions, Try to login in safe mode and uninstall latest updates...
Or try using Different Antivirus - if you are using the free version of AVG, Try using Avast free antivirus version.