I have figured out why this happening, at least to me. Any data macro that is created in a database using version 2010 will automatically result in the above error message if you subsequently try to open it using a pre-2010 version.
To validate this, I took the Northwind example and performed the following steps:
- Opened it in 2007 to ensure it worked.
- Opened it in 2010 and created an "After Insert" data macro in a table.
- (Did not make the data macro event fire)
- Opened it again in 2007
- "Unrecognized Database Format" Error Appeared
So there you have it. That's at least one problem with 2010. Additionally, deleting data macros does not help. Apparently, as soon as a data macro is saved and initialized, it creates an internal structure of somekind that pre-2010 versions of Access are unable to recognize.
Problem #2
Make sure you're not trying to open of the new "web" databases. I have also experimented with these, and none of them that I have will open in pre-2010 versions either. Apparently the cause is again a compatibility issue with internal structure. This is a more understandable issue though, given the fact that web databases are meant to operate on the "web".