In theory, the problem is more related to MS servers load.
So either you wait some time and run the search for Windows Updates manually, or wait for the next automatic cycle.
If that doesn't work, you might try:
Avast GUI -> Real time shields -> Web Shield -> expert settings -> "Scan traffic from well know browser processes only".
I'm not completely sure this setting would solve the problem. If it does, then the "real" conflict might be on the firewall side.
In any case, the best path here IMHO would be to reboot, then wait for the next automatic Windows Update cycle first, then the manual update, and only *then* trying changing settings.