When I open Constraints Editor from within Project Manager, the following Dr. Watson error is reported:
"Exception: Access Violation 0xc0000005, Address 0x0077e950."
When I open Constraints Editor in stand-alone mode for the same project, it crashes as well.
To avoid this error, either attach nets to the floating pads, or get rid of them.
This issue will be fixed in a future release of the software (after 5.1i).