[CentOS] CentOS 5.2 i m having problem with gnome

Hello to all,

I am having a web server mail server Mysql and name server on single machine my os is CentOs 5.2 and desktop gnome everything was working fine now couple of days back I was using text editor, Fire Fox and GIMP at a time and my mouse started to act funny as well as very slow even my keyboard curser moves very slow I feel it is some sort of memory problem but I have noticed the servers are accessible from outside of network are fine except that I am only facing problem while using desk top.

Secondly if I reboot the system it start to work fine for few hours.

I shall highly appreciate if someone can give me a hint or how to fix it.

Thank you.