All: I found that the answer above worked perfectly, but wasn't facile enough for my client, so I wrote a VB application that does the trick. Also, I wrote it so that it pulls straight from the Excel spreadsheet, so no export is needed.
It's in Beta, currently free for trial.
http://devshed.us/Products/FogBugzCaseImporter.aspx
(please up vote this answer if you found it useful)