Lag in UT 2004

Well for a while I have been having a lag problem in ut 2004. I try to just ignore it but considering most of the time I play trial maps its pretty much impossible to ignore it. Basically the game is running perfectly smooth for about a minute or so. All the sudden I am randomly far away from where I was and stuck unable to move for a few seconds. Then it's smooth again until it happens again a minute later. My computer can easily support it, I have an nvidia geforce 8800gt 512mb, AMD Athlon x2 5600+, and 3gigs of ram. I used to not have this problem but now its constantly happening. I have tried things like port forwarding to get it to work right but that didn't work. Does anyone have any idea what I could do to fix this?

Also, I am having a problem with DDR on my computer. In order to get my pad to work I have to install NTPad, however, when this driver is installed numerous games won't run such as Oblivion and UT 2004. Once I uninstall it they run, but I don't want to have to keep uninstalling an installing it over and over. Does anyone know of any drivers that don't conflict with these games that I can use instead of the one I'm using?