No idea what's wrong. And not even sure it's actually wrong at all. It's just i can seed up to 5Mb/s, but i'm not actually seeding a thing now, even though i see 5 peers.
edit: seeding at ~3,5MB/s again. I forwarded incoming connections port in my router again, and suddenly started seeding normally. Why was uTorrent's connection test reporting that "Your network connection is working as it should", i don't know.