No, it will be hard only if the corrupted file is UserSystems.xml.
If the problem is in one of yours databases, you will have only this file to remake.
I know your problem, I have around than 50 systems, some of them are specific and at all update, I need to rebuild all, because the old xml is not compatible with the new executable (Thx mGalaxy ^^).
And if the problem is in UserSystems.xml, you can delete 50% of the file, then 50% again, ect ,,, to locate the problem.