DB - I used BitTornado for a while but have recently switched all my machines to Azureus - prefer the flexibility of the options it gives.
I occasionally get UPNP errors and problems connecting to trackers. Some things to consider that might have influenced this:
1. Do you use DHCP for IP allocation? If so, do you manually specify the IPs for some/ all of the computers in your apartment - by registering a fixed IP for their MAC addresses. If not, you may find that when the DHCP lease expires (or when you reboot the router), a computer gets a different IP that is not matched to the correct rule for port forwarding.
2. In the Advanced section of BitTornado, did you have a range of Ports specified (e.g. 6881 - 6889). I think BitTornado uses a new port for each torrent that you open - so if you have 2 or more on the go at the same time you may exceed the range set in your router. Azureus only uses one port so it is simpler to configure your router.
3. Do you add the port forwarding rules in pairs (i.e. for TCP and UDP protocols)? I think you need both.
4. My Asus router recently got fussy (must have been a firmware patch but I'm not convinced) about accepting the same port forwarding rule for UDP and TCP for a given IP - I now have to specify slightly different, but overlapping ranges e.g:
6880:6889 -> local IP for TCP
6879:6890 -> local IP for UDP
5. Finally, I've come across some trackers that won't accept common BT port ranges (e.g. 6881 - 6889). Worth reading the FAQ on a given torrent site to see if they exclude a specific range.