How can I tell the Android Market that I'm running an updated version of Android?
There are several reasons why apps could be listed as incompatible with certain devices.  It could be Android version, screen size, OpenGL version, camera configuration, touch screen type.  The list goes on and on.  You could try going to Menu -> Settings -> Applicataions -> Manage Applications and force close the Market and Clear the Data.  This would cause the market to download the lastest version of the Market and rescan your phones capabilities.  If that doesn't do it then you may have to wait until 2.2 is officially supported for your device.