Here http://forum.avast.com/index.php?topic=3979.0 i found a solution that makes the outlook Provider work, without disabling the plugin!
“you have to configure your SMTP settings in the Avst setup,
Enter your user name and password.”
After doing this, the plugin started without any problems.
If it works to you also, please post it here, maybe its the final workaround 
Many thanks @Georgev!
I already worked for me without doing so ;D
Avast setup? Do i have to re-install it or do you mean the avast settings?
I’ve tried adding my SMTP settings in avast, but no good, still get this strange bug and what makes it even more strange, that it worked 2 hours ago and now suddenly i get this cant connect to avast engine every single time 
i ment avast settings sorry.
So all you did, was you added your smtp settings in to avast settings?
You didn’t touch anything in outlook?
What i dont get, is how these smtp settings, which avast uses to send email can effect communication between outlook and avast :?
It even says at the bottom:
Note: These settings are used when avast itselv needs to send an email. They are not related to e-mail virus protection.
??
i know
i only did these entrys and nothing more in outlook. i wonder too that this makes the plugin works but it did.
Hello,
A suggestion to the Avast! Developers…
An SMTP and IMAP test would be nice so that at the time the setting is configured, it’s certain whether mail is working or not.
Also, am looking for documentation which client to use… although IMAP is the default, I’m guessing SMTP should be more appropriate in an Exch2K/Exch2K3 environ. Am also guessing (would be nice to find some definitive documentation) that an IMAP client of some sort might need to be installed on the Server (Which is discouraged practice!).
As for the other posts in this thread, they should know that no authentication is likely required if Exchange is configured to permit the localhost to relay anonymously.
Thx,
Tony