Short version: I upgraded from pb18 to pb20 and the wireless interface which
is bridged to my ethernet stopped passing traffic, sort of.

The fix:
1) under Firewall->Rules. click '+' for a new rule
2) change Interface to "WLAN" (or whatever you called your wireless lan)
3) change Source to Type "LAN subnet"
4) enter a description, e.g. WLAN -> any
5) click "Save"
6) click "Apply Changes" on the following rule summary page

Somehow this relates to the DNS and other firewall entries I was seeing in
the log (see earlier message). Somehow, though, some wireless users
continued to surf ok. Probably until their local DNS cache failed.

Apologies if I missed this problem/solution in earlier email. Perhaps this
actually occurred in pb19 which I skipped. (I'd love a pointer to a longer
description fix if so... tia! :->)

cheers, michael