A family of Microsoft relational database management systems designed for ease of use.
If Access says a field does not exist when it does indeed exist it usually means an indexing problem. Start with compacting the database. If that doesn't fix it import everything into a new, blank database. Also compare the field names to what is used in the spreadsheet.
If you still get this error try renaming the field. Make sure it does not have any spaces and is not a reserved word like "Date"