BigAl.
Avast does not "timeout". This is a function of your ISP.
More than likely a lost connection.
I know you said you have the latest version but what version and build do you have? 4.1.335 is the latest.
Home or Pro?
Also, why do you have the outgoing mail scan shut down?
Sometimes, a virus can be part of a larger file, or included with a bitmap file (which can be much larger than jpegs)
This would take a bit of time to transfer from you ISP server to you computer email client.
I am not sure at this point why AvVast did not delete the email immediatley when you clicked "delete".
I can only summize that it was a problem with the data transfer. You were wise to delete it via web.
and yes, I am glad that it works too!
Let me know if you have any other problems with Avast.