The debugger uses $HIBER/$WAKE itself, so debugging a program using
those two routines can be difficult.

Solutions:

1)  press CTRL/C
    DBG> GO @PC+4

    to get the program running again manually.

2)  $ DEFINE DBG$PROCESS NONE

    which will tell the debugger to use the single process version
    (and that version do not use $HIBER/$WAKE).