I got constant Event Log entries for Unknown EDID Version and my boot up would literally take about 5-6 minutes+ to get to the desktop after startup.
After much research I did finally find a fix that solved my problem, though, so I wanted to revive this old thread and list it here in case anyone else is still having this issue.
Go to Start, Run, type regedit to enter the registry. Then drill down to the following registry key:
Make both entries listed under this key a value of 0 by double-clicking on them. Then restart.
This fix was listed on another forum site as simply a means to stop the event log entries for this Ati related error and the Invalid CRT error that is also fairly common. However, when I did it, it also completely fixed the problem, not just stopped the message.