There seem to be quite a few issues with ADE 2.0.
Most can be resolved by uninstalling and reverting to 1.7.2.
As a matter of interest, is it always unstable, or only if you have an eBook reader plugged in? If so, which one?
If you've lost your install for version 1.7.2, it is a little difficult to find,
available on Adobe site for Windows and for Mac.
Either. I think there is a program other than the antivirus interfering with the ADE 2.0, because it runs perfectly fine on my windows xp computer with the same antivirus and an windows 7 computer with a different antivirus. Also, the .exe file was last updated on 9/18 (the day ADE 1.7 was installed) and the other files not in folders in the application folder not sure what they are atm) are all the same way. ADE 1.7 may have a cache somewhere that isn't uninstalling.
Right click on the .exe file in Explorer and choose Properties.
Go to the Details tab and look at product version.
That should tell you which version the .exe is.
My v1.7.2 exe file says Version 1.7; and has filesize 13.3Mb.
If you have got some corrupt mix of versions,
best to uninstall everything, delete the "C:\Program Files\Adobe\Adobe Digital Editions" or whatever directory (if uninstall didn't),
then reinstall whichever version.
I don't see any other cached versions around.