Have you tried applying one of the Noise Reduction Filters? There's actually one called Hum Remover where you can adjust the frequency of the sound you wish to remove. I'm using Final Cut Pro 6, but I suspect it's also there in FCP HD too.

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Lloyd

That's my opinion. If you don't like it I have others

System: Apple Macbook Pro 17, and an external Freecom 500GB eSATA drive.
Software: Final Cut Studio 2 (FCP 6, Motion 3, Soundtrack Pro 2, Color, DVD Studio Pro 4, Compressor 3), Sonicfire Pro 4.5
Favourite Resources: Findsounds.com, Free DVD menus, Ken Stone's FCP Page, Wikivid