Some bugs i have found today while playing, hope they help.
1. Wrong Race displayed in AI Comes to Aid dialog after race declares war on player (think this might only apply to the Alterian's due to their Super Ability). Screenshots:


2. After decommisioning a improvement and then trying to rush buy a new improvement the wrong improvement can be built. Duplication steps:
a. Decommision a Tile Improvement
b. Select the Tile and place a new improvement
c. Select a different tile improvement in the "projects" list (which should now be grey)
d. Press the "Buy" button. The improvment from the "projects" list is built instead of the one placed on the tile.
3. I tried installing the gc II + dc beta on my Windows Vista x64 RTM (from MSDN) installation with the latest beta of the NVidia drivers (v 97.27) and found that the game has some extreme performance issues if the Context Menu is not hiden. Once the main bar is hiden however the game runs very well however it does making playing rather difficult.
Please let me know if you require any more information.