civ 4 graphical gliches

[Jayrad]

I have benn playing Civ 4 for a year now almost and just a few weeks ago it started to have graphical glitches where the UI and stuff will start flashing and its hard to play without that. These start to happen towards the end of the renaissance ages.

CPU- Duo core prosesser = to 4.1 ghz
RAM- 2GB DDR2
Graphics card Nvidia Geforce 9500gt with 1g video memory

Any fix will be apreiciated because civ is currently unplayable for me