OK, so I started the experiment and soon got pulled up. I'm saving my .xls
file as a binary .xlsb, and the darned thing wants to put an underscore in
front of range names. I dunno if it applies to all, but the first one not
acceptable was Bal001. Aah yes, would this be because Bal001 is now an actual
cell within the new Excel 2007 spreadsheet size?

I've got a feeling that's probably the case. If so are there any other new
restrictions on range names since Excel 2000?