My port forwarding closes itself for no reason

[seladoor]

I've never been reduced to posting in a forum for help before; I can usually find the resolution using Google, but this seems to be an unprecedented problem.

I am wired to a Wrt54gs Ver 6. router (I know that it's crap) and I use Virgin media 20Mb internet (speed tests give me 15mb DL and 850kb UL speeds). The problem I have is so strange because it will close my opened ports all the time for no reason. The wierdest part is that when I go into the routers settings and click 'save' (without changing any settings whatsoever) and then test the port range forwarding, it's suddenly ok again.

The problem is probably coming from the router, but it's such a strange situation. It's almost as if the router is forgetting the saved information it has, although this couldn't be true because it also holds all my wireless security information for my laptop to connect.

Any help would be appreciated but I suspect most people will tell me to buy a different router

[GTHK]

Make sure UPnP is disabled in µT, if it is, make sure no one else on your network is trying to map that port. If that doesn't work, try disabling UPnP in the router.