If you're on the PS3 - put the PS3 on the DMZ host to give it all port access.
D/C and 90k errors stopped happening to me. Rarely a few will still pop up but that's unavoidable.
Also - check if you have/get a Gigabit router.
Older routers cannot handle sudden surges in data connection and cause disconnects.
(A good example is trying to upload a large file with multiple connections - Gigabit routers can handle this kind of load)