This is straight from Toontown Test Known Bugs
Known Issues
Here are a few issues (bugs) that are under investigation.
Black Screen instead of Login Screen
We are investigating reports of a Toontown startup problem where only a mouse cursor is displayed over a black screen when you should see the Toontown login screen. We believe this is not a graphics problem but a case of the Toontown program waiting for a message from our servers. If you see this problem and Toontown fails to respond for over a minute, please hit Alt-F4 to exit, and immediately submit a bug report. It is possible that simply restarting Toontown at that point will work properly. If this is the case, or if you perform some other action such as rebooting/installing new drivers/uninstalling and reinstalling Toontown that causes this problem to no longer appear, we would like to hear about it on the bug report page. Switching to a less populated district after you log in successfully may lessen the chance of this occurring when you restart the game.
Memory Leak
After playing for an extended period you may notice that the hard disk drive is being accessed often ("thrashing"), and the game gets slower and slower. Toontown currently has a problem "leaking" memory, which causes it to use progressively more memory over time, which eventually causes the OS to 'swap' RAM to disk in an attempt to allocate more. If you experience signs of this, we suggest you exit and restart the game immediately (using Alt-F4 if necessary).
Random video graphics problems
If you see many polygons being drawn in completely random places turning Toontown into an inscrutable collage, first check with your graphics driver manufacturer's website to make sure you have their latest video driver installed. Windows 2000/XP users, please install the latest MS Service Pack for your OS (available here). If installing all of these fails to correct your problem, please run C:\windows\system\dxdiag.exe (or c:\winnt\system32\dxdiag.exe), click 'save all info',and send the resulting text file along with screen capture images (press F9 in-game) demonstrating the problem to
toontown@disneyonline.com.
Mouse Cursor Problems
If you have an ATI card, are running Win2000 or WinXP, and see a black square instead of a cursor, this is due to an ATI driver problem. If your cursor flickers or flashes on and off as you move it across the screen, this is also a video driver problem. Please download the latest video driver from your card manufacturer.
Transparency Problems
Sometimes you will notice a 'black' background behind items such as the snowflake, or things like mist clouds will partially disappear when you get close to them or look at them from certain angles.
Camera Shaking
In certain locations the viewpoint will bounce back and forth between two positions very quickly, causing an 'earthquake' effect on the screen.
If you reply to this post, please keep it to comments relating to the above bug list... -rcv-