This afternoon, I was working with Access 2010 on an Access datafile that was created and is in production in an Access 2007 / Excel 2007 environment. There is inter application Automation - VBA in Access has a reference to Excel. Things seemed to be working smoothly until I noticed some odd glitches. On one Access 2010 machine, certain parts of code would not work - the error message was something like "unknown database object". On another Access 2010 machine, the DATE() function gave an error. Checked the object library references in the VBA IDE. Found that Excel 14 / Excel 12 alternately were missing in action. In the relevant Office version, the Excel Object Model Library was there, but not automatically ticked, while the wrong, missing Excel Object Model Library was.
After a while, I avoided using Access 2010 to develop the project.