Games run extremely slowly
The main cause of this is that you are running on a system whose video drivers are not optimized for DirectX. One way to fix this is to visit the web site of your video card's manufacturer and locate the most current drivers for your specific video card. One indication that the drivers are the problem and not the games/engine themselves is that some other 2D games will also run slowly (Game Maker games for instance).
Overflow error occurs after a period of time in the map
The most frequent cause of this error is a sprite on the map that fell off the bottom of the map and was not deleted. One way to make sure this doesn't happen is to make sure all your sprites are set to delete when they are off the map. Another way is to make sure all your sprites have a solidity definition set, which will make sure they can't fall off the map (because then it will see the edge of the map as solid).