In the last couple of years I received several cases related to problems when using "stsadm -o restore" or "Restore-SPSite" commands.
The users received an error message similar to the following:
Your backup is from a different version of Windows SharePoint Services and cannot be restored to a server running the current version. The backup file should be restored to a server with version '1262884508.196508.17294360.0'
The version number in the error message varies but is always a very big number which is not at all a version number for SharePoint.
This error occurs whenever you are trying to use a file which is not a SharePoint backup with the restore command - e.g. a SQL backup or a SharePoint export file. SharePoint tries to read the version information from the file header of the file - and if the file is not a SharePoint backup file the data at the location where SharePoint expects to find the version information is usually something completly different.
In most cases the relevant files were either SQL backup files or created with STSADM -o export.