CLJ 4500 duplex printing from Word 2000

I just installed a duplex unit on a HP Color Laserjet 4500 along with 32MB
of extra RAM. Everything looks ok when i print a configurations page.

The duplex unit and the extra RAM has been correctly configured in the
driver.

Printing in duplex from Excel 2000, Acrobat Reader and other applications is
no problem - the printer prints on both sides off the paper.

The problem is ONLY when printing from Word 2000, and choosing duplex
printing (the EXACT same way as if I print in duplex from e.g. Excel), the
print still comes out on TWO sheet, instead of on both sides of ONE sheet.

What am I missing? I tried on several client machines (Windows 2000), with
no luck.

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Esben