I have read several posts from Alwil members saying only the problem with the key was fixed in version 4.5.561, but if I understand correctly what Vlk says here http://forum.avast.com/index.php?topic=9435.msg79944#msg79944 this is also included in the latest version.
Is it or is it not included?
No, it’s not. The program modules in 561 are exactly the same as in 549; the (key problem) fix was done to the setup component only; therefore, updating 549–>561 didn’t require a reboot.
The problem with the keys was a very bad one, so it has to be solved immediatelly - and fortunatelly, it could be performed only by changing the setup part. The new version of avast! is really not ready yet, so the program files were not modified (they are in a “working state” right now).
I think Vlk should regenerate the checksum for the mentioned hotfix for build 561 - so that avast! would accept the fixed file (which is now turned back to the original version by the “autorepair” function, I guess).
Thanx for the explanation. Now it is clear to me (and others?). 
The file http://www2.asw.cz/~vlk/Aavm4h.dll.sum has now been modified to work with build 561.
Thanks
Vlk