Step 1 :

Join two channels.

Step 2 :

query nickname

Step 3 :

dcc chat nickname

On dcc chat window opening, the background for the query window will disappear. i.e. the gif/jpeg you have assigned will be lost, and the default background color will appear.

I'm not sure what else I can add, but it's something that happens virtually every time I connect.

I have a clean WinXP system and run Sophos antivirus.
Thanks
-Ivan.