It is probably caused by the spaces in the names of the project file and path. Try replacing these to see if the issue is resolved.
Tried this already, didn't work. Also, I have many projects with spaces in the project and path and have never not had them compile. I have read mentor software doesn't like that but it has never been an issue for me.
try to close all schematic tabs and try again.
I have this problem sometimes, when i open the DxDesigner out of PADS over Tools-> DxDesigner->Connect.
Closing all the schematic sheets solves it most of the time.