Tray icon has a stop sign superimposed over it

Hello, Could you explain why the TRAY ICON has a STOP SIGN superimposed over it - a RED CIRCLE with a RED LINE diagonally across.
I opened the firewall and it said everything was working O.K. and I did not have to do anything!
I am a basic newby and I am worried what is happening.
Also I wish you would put up an explanation how to post.

I am running an ACER Laptop 9500 series with XP HOME and AVG FREE version 8

Could you please email your reply as I don’t know how to read your answer on the FORUM

Thanks, Bob Webster - bob@chcmail.co.uk

Topic split and moved from Introduction from the CEO of Comodo. (:m*)

LA