Level Check
From MidrangeWiki
A level check error indicates that the file the error is being reported on has changed since the last time the program that is trying to access the file was compiled.
This is the systems way of protecting itself from errors introduced by buffer layout differences between the program and the file.
Level checks are caused by the format level identifier for the file not matching the coresponding identifier that is embedded in the program being run.
(we need more here)
