When creating ODF-based spreadsheets, Excel 2007 also saves formulas in a nonstandard location, Weir said. That causes other spreadsheet programs to also fail to read the data properly.

Weir fixed the blame squarely on Microsoft.

"The degree of incompetence needed to explain SP2's poor ODF support boggles the mind and leads me to further uncharitable thoughts," Weir wrote.

Microsoft assigned fault, however, on the latest versions of OpenOffice.org and Symphony that write formulas according to the ODF 1.2 specification. Office 2007's recent update supports ODF 1.1, which is an approved standard. ODF 1.2 has yet to be approved by the nonpartisan OASIS standards body.

When ODF 1.2 is "completed, standardized, and published, we'll be looking at that as the future path for enabling formula interoperability in ODF spreadsheets," wrote Microsoft's senior program manager for Office interoperability, Doug Mahugh, posted Tuesday. "But we're not there yet."