ports closing on me

Ok, i use a p2p app (soulseek) as well as azureus for torrents. I have correctly forwarded my ports, but after a few hours of the computer being on, the ports decide to close themselves off, as the built-in test on soulseek and azureus will confirm. I am using a Vista machine, and never had a problem with this happening on my XP machine. Has anyone else had this problem, or does anyone know what might be causing this to happen ? Its quite frustrating to have to restart my computer every hour or two to get my ports open again (the only way i have figured out how to re-open the ports). I just cant figger this 'un out.
:confused