I installed ScreenRecycler.1.38.(1000702).dmg today and after reboot, the login screen does not show any users making it impossible to login. I'm told by screenrecycler.com that this is a bug in Lion that causes this problem with ScreenRecyclerDriver on some hardware, but not all.
If you get this problem, boot in safe mode (hold the shift key and power on). This will let you login as usual since the ScreenRecycler driver is not activated. As root, navigate to System/Library/Extensions and delete ScreenRecyclerDriver.kext. Then restart normally and you'll be able to login again.
