Word does allow a table to be used in a document with a multi-column layout. Evidently, then, either the way you're going about it is wrong or there is something else about your document's setup that you haven't told use that is causing problems. Without actually seeing the problem document, though, it can be difficult for anyone to diagnose the issue. Can you attach a document to a post with some representative data (delete anything sensitive)? You do this via the paperclip symbol on the 'Go Advanced' tab at the bottom of this screen.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]