Are you using windows 2000/XP? If not, you experienced the typical windows 9x resource problems. It seems that Windows 9x does not correctly free reserved memory. I have the same problem here on my WinME computer, also had this with e.g. Bearshare before. After a few hours running Bearshare/Xolox the system gets very slow (might be same with any other client too), due to page swapping. So after a night sharing I have to restart.
Here's a sheet which shows a typical Win9x CPU/memory usage:
(I made 3 shots each running Xolox/BS for ca 6 hours)
PS: I serve the image a while on my webserver, here is a backup attachment: