Although I'd love to see everyone upgrading to Office 2007 across the board, and especially see them get Office Enterprise so they get Groove 2007 too, I know that there are some customers that need to remain on Office 2003 for a period of time. Some of these customers have asked about running Groove 2007 alongside the other Office 2003 applications. This is a supported configuration - Groove 2007 does not have a dependency on the rest of the Office applications. And although Office Groove 2007 has some great integration with SharePoint 2007, Office Groove 2007 doesn't require SharePoint in any way. either.
We recently uncovered a bug that manifests itself when a customer has installed Groove 2007 and is using Office 2003. When the user tries to access certain SharePoint functions, such as Office files on a SharePoint Site, Internet Explorer 7 will crash. This is due to a visioning issue with mixed DLL versions of MSO.DLL and OWSSUPP.DLL
The issue has been hotfixed and will be included in SP1.
The kb article and hotfix download is available at http://support.microsoft.com/default.aspx?scid=kb;EN-US;938888.