windows installer pop-up message when I run Avast scannner

Hi.

I was infected whit Trojan Vundo, but a remove it and now,
When i run the scanner a windows installer window appears
and the scan don’t start if I don’t cancel de installation or I let it
to complete.

I uninstall and install avast, but the problem persist.
What can I do?

Heeeeeeelp!

Note.
I have Avast 4.8 personal edition and the pop-up appears
when a try to open somo Windows office applications