Somewhere this week I changed my firewalling script so that on start it would clear out all the tables and start fresh with my rules. Some time afterwards I noticed I could not reach certain sites, such as Ebay, modules.apache.org, mininova, and others – I didn’t see the connection immediately though.
When clearing out the rules it also automatically cleared out the “clamp mtu to mss” option Debian’s pppd script enabled before… after putting that back into the tables, everything started to work fine again.
Took quite some debugging, as I first thought this was a pmtud issue, and that was supposed to solve it… Another thing learnt, another thing to remember when similar problems arise 🙂