You can try to exclude the Website.
Open avast!
Click on REAL-TIME SHIELDS
Click on Web Shield, click on the Expert Settings button
Click on Exclusions, pres the F1 key to get help with exclusions:
On this page you can specify URLs and MIME types that should not be scanned by the Web Shield. This can be useful when downloading a large number of files from a single, trusted source.
URLs to exclude - Use the "Add" button to enter the URL addresses that should be ignored. If you want to exclude only a single page, you need to enter the full address e.g. you would need to enter the full address
http://www.yahoo.com/index.html if you want to exclude the page index.html. However, if you enter
http://www.yahoo.com/* no pages starting with
http://yahoo.com will be scanned. If you want to exclude a particular file type from being scanned, e.g. files with a ".txt" extension, enter *.txt.
MIME types to exclude - Here you can specify any MIME types/sub-types that should not be scanned.