try going into your routers settings and disabling UPnP, i have had problems like that before and they stopped after turning that off. you may have a different router then the linksys wrt54gs or but this will still help. atleast with setting up/getting the port numbers needed for PSN. goto the 4th page and its the 3rd to last post, with all the pink writting/corrections the poster made.

http://boardsus.playstation.com/play...sage.id=215782