"Compile error in hidden module: This WorkBook" only appears when project locked

I am getting the error message "Compile error in hidden module: This
WorkBook" when I try to run an Excel VBA macro from a toolbar button.
I looked around and found that this happens when a project is locked,
so I unlocked it, expecting to be able to debug now, but surprisingly,
now it works. Unfortunately I cannot allow these Excel macros to be
distributed unlocked because they contain clear-text passwords. It
only happens when I launch Microsoft Excel 2003 normally; if I
directly open the .xls file that contains the macros, it works fine.
Is there anything I can do?
.

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