I guess the problem was the huge patch day from microsoft three weeks ago - they managed to make some of their own products unusable with that and I am sure they also screwed with third-party programs. They are in the process of fixing some things they broke - but I guess that'll be a while.
is this just civ4 and bts or also warlords?
what I would try is a complete reinstall - but please do not do so before I post a howto
Hmmm. I had no issues from the big patch day. I've been reading on a Windows forum lately about a large upsurge of lag problems involving Nvidia users. It looks like some of our fellow Civ Fanatics are having trouble as well, and many of those folks are using Nvidia cards.
It looks like the new fixes (and Windows 7, too), have caused the lag issue, though it doesn't seem to happen with Radeon cards quite as often.
Note that if you are using Windows 7, the graphics engine in Windows has been changed from XP, and particularly Vista. Windows has retreated from Vista's software-oriented rendering routines, and gone back to using some of the hardware acceleration that was used in XP, and is native to the current video cards. To that end, you shouldn't use graphics drivers made for Win 7, in a machine that isn't running Win 7. It's best to use the ones that are specifically designed for your OS. What worked on Vista before, will still work now, for example. ATI gives you the choice of OS specific drivers, but I'm not sure about Nvidia. The general consensus around the Windows forums is to not upgrade your graphics drivers unless you have to, and to make sure that DirectX is up to date.
I made the move to Win 7 last week, and I have had almost no problems with Civ (aside from the initial install, which I will post about shortly.) I have not experienced any actual game play issues. It works the same as on Vista and XP, so I guess there is some good news there after all.
Stay tuned, Lemon Labs is working on the problem.
try a newer graphics driver: 
