There’s a known issue related to restoring a database. If you exported a MySQL 5.1 database and tried to import it into a MySQL 5.0 database, you’ve quite possibly been bitten by this.

The fix for this issue is …

Use mysqldump from the command line:

mysqldump -hHOSTNAME -uUSERNAME -pPASSWORD –compatible=mysql40 DATABASE_NAME

After dumping your data, try importing into the 5.0 database again and you should have no trouble.

The problem boils down to this:

  5.0 supports only the following syntax for key definition (see "CREATE
  TABLE syntax" in the manual):

  {INDEX|KEY} [index_name] [index_type] (index_col_name,...)

  While 5.1 parser supports the above syntax, the "preferred" syntax was
  changed to:

  {INDEX|KEY} [index_name] (index_col_name,...) [index_type]