Hibernate password not recognised

I have found several users on Google with this problem - but no answer. Any
bright ideas to this one.
A Windows XP Pro fully patched, peer based workgroup machine. With a single
user account that is password protected. Normal startup and shutdown works
OK.

Selecting Hibernate shuts down the machine with no fault. On resume however,
XP refuses to recognise the user password. Recycle the machine to a normal
startup, and the password is recognosed.

Attempted to alter password, cycle hibernate mode on and off, and create a
new user account. All with the same effect.