After getting a lot of 11055 type errors in my connection, making it impossible even to browse the web, I made a:
netstat -an
and saw a lot of connections with a certain IP address:6969
and as I suspected, that IP address turned out to be the tracker's.
After closing BT, those open connection were still there (only the connections with peers and seeds did disappear), so I rebooted and started making some tests.
This happened with version 5.8.11, so I tested the newest BitTornado 0.0.1 and still happened, then I tried good old 5.8.7, that I've used for the longest time without any problem but the bug was still there. Open connections with the tracker accumulate as time passes, each one using a different port on my side, until you close the program or the maximum number of allowed connections is reached. When that happens, the number of peers & seeds usually starts to decrease, because sometimes a connection is closed and (I guess) the available connection is taken by a fake one.
After closing the program, the connections are left open, but that's because, as stated in this topic:
http://forums.degreez.net/viewtopic.php?t=81
the closing wasn't correct, and killing the dead btdownloadgui.exe, those connections are finally closed.
This problem only seems to happen with
certain torrents/trackers, because I'm downloading other files now and it isn't happening. But I've been observing the degrading behaviour (reaching max number of peer connections, then that number slowly coming down and not recovering) for a while now, and I suspect it's related to this bug.
In case it's useful to fix the problem, I'm using Windows 98SE and I'm firewalled by my ADSL router, but I've opened port 6881 and therefore can get the green light (as long as I use just a torrent at a time). I have the maximum number of connections limited to 20 and the problematic torrent tested was this one:
http://a.scarywater.net/aone/[AonE_N!]_Hunter_x_Hunter_GI_FINAL_OVA_-_Ep_02_[112097E5].avi.torrent