I thought I remembered seeing that this had been fixed--whenever I get a whisper from an AI ally (say), or the 'Planet <name> acquired' message, or anything else in the chat text area at the top of the screen, my framerate drops drastically.

Using the 181.22 GeForce drivers and an 8500GT. Dxdiag available on request--I don't like to pack it into the first post in a thread.

I fiddled around with graphics settings today. It seems much worse on the Non-maskable antialiasing setting. Too, turning off bloom seems to make the problem almost entirely go away.

That may just be my graphics card breathing a sigh of relief, though.