I don't know if the spam filter is relevant to the error messages. Avast can be "partially" (un)installed, and so some shields / modules / components are not installed at all.
I think the problem requires some input from Avast Team developers. All other input is just speculation (even if there could be some partial feedback from common users, it won't truly answer the main question here).
IMHO, you have a couple of basic possibilities. You could wait for some developer to come here to help you (and there is no way for us, common users, to know when they would do it, specially while they are currently focused on avast 7 beta).
The other possibility is to save a copy of all the relevant info (dumps, logs, errors, reports, Windows event issues,
avast license file,...) and uninstall avast. After the normal uninstall, run the removal utility several times with reboots in between. For each run, you select each version of avast ever installed (or updated to) in that system.
http://www.avast.com/uninstall-utilityYou could even go beyond the removal utility. After running it several times as described, you could manually search for any (hidden) folder with "avast*" or "alwil*" in its name, and delete it.
Then you could install the latest stable version of avast. If you (or your friend, actually) have AIS, then download AIS TRIAL. Install it, reboot and test it. If it works, then use the copy of your license file (remember above?) to transform the trial into a registered version.
The problem with this option is that it erases all previous traces of the problem, without giving you any indication that the problem will be solved after the clean install, and the developers will have less info available to solve it (hence, I strongly suggest backups of the relevant info, and of the emails and contacts in Outlook).
There is a third "middle ground" possibility. You could wait some more days for an Avast developer to post here, while you wait for avast 7 (instead of reinstalling avast 6 ). It will get out as beta first, and I can't assure you that an avast developer will actually look into this (they should, as a paying customer). Avast 7 (either beta or final gold) "could", potentially, also solve the problem, but as already said, we common users are not in position of helping you (the specific error you get is not listed nor explained.
In any case, you should open a bug ticket report at
http://support.avast.com/index.php?_m=tickets&_a=submit.