Use the "/PERSISTENT" switch on the delete - this will often help.
You should also check the result of the add and delete (see the @ERROR and @SERROR macros). If @ERROR is not zero, print the values out - this will give you a clue why the add or delete has failed.
Just follow each of the USE commands with something like:
Code:
If @ERROR "Error deleting mapping: " @ERROR "/" @SERROR ? EndIf
