I have an excel file that contains 5 sheets ( 3 of which are set to
veryhidden in the properties ). The other 2 sheets are for
inputting/validating a username and password and a results sheet. Navigation
between the sheets is by buttons ( with macros).
The file is updated weekly and placed on our website for endusers to download.

The user opens the file and enables macros (security setting has to be
medium - it doesn't work when set to low), inputs a filepassword, and enters
their username and password - this is verified by a VLOOKUP function. The
User selects SUBMIT button - the macro behind this, produces a individualised
results sheet based upon the username and password.
There are also buttons(macros) to clear entries and return to username
and password sheet.

I have 1 user out of nearly 1000 (the other 999 users have no problem) who
opens the file correctly, enables macros, inputs their username and password
(which is verified), but on clicking SUBMIT, and therefore running the macro
gets a VBA error message (I don't know what this is), but also gets
'navigated' to the result sheet (which is part of the macro), and also sees
the hidden worksheets ( ie the property must have been changed).

I don't know what is happening, but would appreciate any suggestions.