Emma, wellcome!
We’re glad to receive you in this family! 8)
Specially an avast full user!
Well, sometimes in the past I have the same problem.

Let me guess a little:

  1. How are your timeout configurations? (both in OE and avast)
    If you set large values could solve the problem (specially on dial-up connections).

  2. Do you use any Spam killer (like Spamihilator, for instance)?

Well, Techie was faster than I (as usual) and he tries other possibilities.