OpenOffice cannot currently handle (Microsoft) Office Open XML files (http://en.wikipedia.org/wiki/Office_Open_XML
) which is what Microsoft Office 20007 produces by default. (Well sort of. The specification that Microsoft submitted to ISO for certification isn't the same as that used by Office 2007. That's Microsoft for you...) OpenOffice 3 will be able to handle such files.
Novell do offer filters that give OpenOffice 2.4 the ability to read/write (Microsoft) Office Open XML files however the Linux version says it only works with openSUSE or SLED and then only with the Novell edition of OpenOffice. http://download.novell.com/Download?...d=d3PAMYmvjOg~
Your best bet is to re-save your files in to Microsoft Office 2003 or XP formats and save all future files in these formats.