That's a new one on me. First thought that comes to mind is that the PC the tables were linked with has a newer version of the ODBC driver than the problem PC's. That of course assumes you have tables linked to SQL Server as the message implies.
All 6 users had MS Access 2010 and the SQL Server ODBC Drivers installed at the same time by our IT Department. I will have to confirm that they are all the same version but I suspect they are. All 6 users have Windows 7 but I'm not sure if all have 64 bit or 32 bit or a mixture. I will check that this afternoon. Also they all connect to SQL Server 2008 R2