losing rollovers and ability to type chat

[mercurycs]

I have had the same problem since the pre patch days. I lose the ability to type chat with my buddies sometimes. I type but nothing shows up and if i happen to hit a keyboard command for anything while typing it messes with the game by doing the command instead of putting letters in my chat box. also I seem to randomly lose my rollovers when selecting what to build in my cities and other rollover spots. I can alt-tab out and return to the game and it fixes both problems but I want to try the new memsaver option in the ini and that will disable my alt-tabbing ability. Also, if I play in windowed mode I can't get the problems fixed by alt tabbing. anyone else have this problem?

winxp pro
amd athlon 2800+
1 gig ram
radeon 9200 8x agp 128 meg video
civ 4 1.52