Microsoft rebuffed the charge, while an industry analyst called the spat an overblown issue that users of ODF-based productivity suites, taking the right steps, can dodge.

Excel 2007 and other parts of Office 2007 began supporting with the release of Office 2007 Service Pack 2.

But according to on the personal blog of Rob Weir, chief ODF architect for IBM, Excel 2007 "silently strips out formulas" when reading spreadsheets created by other ODF-compliant programs, such as OpenOffice.org and IBM's Lotus Symphony.

"This can cause subtle and not so subtle errors and data loss," wrote Weir, as results dependent upon dynamic calculations -- today's date, for instance -- become inaccurate.

This data loss is also true when Excel 2007 tries to read spreadsheets created by Microsoft Office 2003 with the aid of a Microsoft-sponsored plug-in or one from Sun Microsystems Inc.