If looks like Google have just changed from Office 2003 to Office 2007 as their default export format.
We have asked them for more details and will upgrade Syncdocs handle it correctly when they confirm it.
For now Syncdocs handles both Office 2003 and Office 2010/2007 formats fine. Hoiwever, Excel will ask for confirmation before loading it.
Office 2003 users may need to install the free compatibility pack