For some reason whenever i join a NS server this thing appears...
http://img296.imageshack.us/my.php?image=nsprobfn8.png
The letters are all green,
the background is darker,
the spectator and readyroom is really dark...

I just had a new PC and installed NS, and these are my specs.
OS Name Microsoft® Windows Vista™ Ultimate HP
GeForce 7600 256MB with dedicated video memory
2GBs of ram
Processor Intel® Core™2 CPU 6420 @ 2.13GHz, 2133 Mhz, 2 Core(s), 2 Logical Processor(s)

If you need more specs ask me, thanks.

try reinstalling NS.

btw I love you ultimate.....

look here at point == 2. Natural Selection, and 64-Bit Operating Systems. ==
Common Problems

That is due to windows vista mate, my brother and his friends had exact same problem... the only way to fix it is to use windows XP