Debugger weirdness

My officemate is debugging a program with some code something like this:


C GROUP SETLL RECORD
C IF %found()
C READE GROUP
C MOVE SSUSER USER
C* ... do something for each user
C MOVE USER OTHERVAR

The strange thing is that after the first MOVE, issuing EVAL USER results in a 'syntax error' message. USER is filled with the expected value, because the second MOVE works as expected.

Is 'USER' a special word in the debugger command line language? Any other ideas?