Opening a project created in ISE 10.1, with Project Navigator 10.1 displays a pop-up message stating that the project needs to be migrated to the latest software version.
When a Project Navigator project is saved, the version of the ISE software is saved in two different areas of the project file.
When a project is opened, the version information is compared against the current ISE version and if there is a mismatch, migration is invoked.
If a new project is created, but somehow closed before it gets a chance to save the project properly (e.g., Fatal Error, system outage), the version information might not get written to the second location.
The ISE 10.1 code only looks at the second version location, and if this information is missing, it calls the migration process.
This problem has been fixed in the latest 10.1 Service Pack available at:
The first service pack containing the fix is 10.1 Service Pack 2