I have the same problem, especially with complex economy. Im on Vista 32.
I have another problem : when i launch the game, scrolling using the middle mouse button, or placing the cursor near the edges of the screen, work perfectly ; but as soon as i enter the military advisor section, and i click on one of the corps, when i go back to the main map mouse scrolling doesnt work anymore AT ALL : no edge scrolling, no middle mouse button scrolling.
And the last province i selected before entering military advisor menu stays highlighted in green, no matter where i click.
After i end the turn, everything gets back to normal.
I must say the game is running slowly, scrolling is slow, battle movements feel slow too ; heck, even clicking somewhere feels slow : i click and the button is highlighted only a second or so later, especially in the military advisor section, where i must click like 4 times to get anything selected. My computer specs should be far than enough to handle it though : Dual Core 2,6 ; GeForce 8800 GTX ; 2 gigs of Ram.