incorrect key file for table

MySQL Version: 4.1.10

I am loading a temporary table in a MySQL database from an Access database.
The Access database has 245 records in it and when I reach record #245 I get
the error incorrect key file for table 'tblTempClasses';Try to repair it and
any records following record #243 are dropped. I'm dropping the table and
re-creating it each time and I know it has nothing to do with the data
itself because I can change the sort and the problem then appears on a
different record but it's always record #244. The table is corrupted and the
REPAIR TABLE does fix it but what is causing it to get corrupted preventing
me from loading the entire table?  Here's the table structure:

CREATE TABLE `vic_showsec_com_tblTempClasses` (   
                                  `ClassSelected` enum('ON','OFF') default
NULL,  
                                  `ClassNumber` varchar(11) default NULL,

                                  `ClassDescription` varchar(100) default
NULL,   
                                  `ShowNumber` int(11) default NULL,

                                  `ClassPrice` decimal(5,2) default NULL,

                                  `ShowID` bigint(20) default NULL,

                                  `ClassDate` date default NULL,

                                  UNIQUE KEY `ClassNumber` (`ClassNumber`)

                                ) ENGINE=MyISAM DEFAULT CHARSET=latin1     

 

Vic