Ace stops downloading data after some time. That's with 500Mbit/s net.

First of all, it really gets on my nerves that Ace stream is playing tricks on me with this connection:

http://www.speedtest.net/result/3411509709.png (500/500Mbit/s)

I don't have any issues running 2 HD instances of sopcast which takes 20Mbit/s up/down combined, yet with Ace, it plays fine for some 20 minutes, then all of a sudden speed gradually drops to 0.
When I try to restart the stream, it buffers, but then just plays cached fragment from HDD, and not the actual stream, when the cache ends, it just stops once more and the circus continues in this loop. If I somehow manage to restart it, it happens again, sometimes buffering kicks in playing on my nerves as well :D no matter

What's going on? I would think the router is the culprit, but everything is forwarded properly, upnp enabled, and when it works, it works OK, upload speeds alone above 20Mbit/s are not unusual for it, but then all of a sudden it stops...
I've tried changing number of connections, changing ports etc.. but it all makes little to no difference.
I would have tried to enable upload limit, but it seems that devs broke that feature on purpose as it never works.


What's going on? Any ideas?