Before you updated to Snow Leopard were you using a different version of Helvetica? I.e, was a different version of Helvetica installed on the Mac (other than the one in the System folders) and was the document using that version?
I ask, because your upgrade would have installed a new version of Helvetica into your System folders. OSX installers (all versions) do that by default.
If you were using the System font then your font caches might be corrupt. Font Nuke can clear them on Tiger, but I'm not sure how to do that on Leopard, much less Snow Leopard.
Erik Youngren (Click my name to email me, or the Contact button above.)Composing: Pueblo Publishers
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