How/Where did you see this in W7 ?
Control Panel ->
Internet Options ->
Content ->
Certificates ->
Trusted Root Certification Authorities tab.
There is no option to remove this certificate.
You may want to re-import and delete this per the FAQ.
That reference only discusses Thunderbird, SeaMonkey, and The Bat clients. To the best of my knowledge there is no function in Outlook to delete or import the .der certificate that Avast exports in accordance with the instructions on that page. I was able to import it via Control Panel, but it did not replace or delete the "Avast Mail Scanner" one already there.
Hold down CTRL key and click on your Outlook icon to launch Outlook.......this will run it is SAFE mode (ie. no Avast add-in).
Same issue ?
Yes.
Also, did you try to set within Outlook ?
Yes, but unnecessary; setting it in Default Programs does precisely the same thing. Yes, it was already set. And as noted above, I just installed Avast Pro this morning - and the problem did
not go away.
HOWEVER, additional information:
Further testing indicates that the error message appears not quite when I start Outlook, but when the add-on Outlook4GMail tries to sync my Outlook contacts with GMail. That add-on was updated this week, and the reason had to do with a change in GMail itself (specifically, the Calendar API). There may be some remaining incompatibility; the add-on is doing what it is supposed to (syncing my calendar and contacts) but seems to be generating this error. I have now submitted a help ticket with the source of that add-on.