Open AVG control centre, double click on the email scanner window. Click on the configure button and you will see the window is divided into three sections.
Email scanning. Tick the top 4 boxes of the 6 on show.
Scanning Properties. Tick the top 2 boxes of 3
Attachment filter. Tick the top box of 2.
Click OK then click on the General tab, place a tick in, Display component and click OK.
If this fails to work then open the email scanner again and click the, Disable Plug-in button lower right of the window. Post back please and let us know how you get on.