One way connection?

[Sidicas]

Sounds like you're getting a lot of upload packet loss.
There should be tools and tests that you can run to check out your upload packet loss.
99% of the time it's an Internet Service Provider problem. Especially a big problem for Cable Modems in areas where Internet Access has been oversold.

I used to see that a lot in First Person Shooter multipler games. A good ping is worthless if your Internet Service Provider is dropping your packets because there is too many people running BitTorrent uploads in your town and they just dont have the backbone for it.

I've thought of a couple other things it could be, but each more unlikely than above.. It's possible it could be that your router has a buggy QoS implementation and it's your own router that's dropping the packets. Try turning QoS off at your router if it will let you.

...and if you're using Wi-Fi, try switching to a wired connection to make sure it isn't your Wi-Fi connectivity that's having a problem. If one of your neighbors turns on a Wi-Fi router on the same channel, you're going to have a bad time from the interference until it can switch channels (automatic by default but some routers are manually configured by their owners to stay on specific channels and expect other wifi routers to just move out of the way).