Got error 124 from storage engine

[P S]

Hi there,

Following is my table definition:

CREATE TABLE `User` (
`DefAcct` varchar(32) default NULL,
`Email` varchar(64) default NULL,
`Fax` varchar(20) default NULL,
`FName` varchar(32) NOT NULL default '',
`Id` varchar(50) NOT NULL default '',
`Pwd` varchar(50) NOT NULL default '',
`LName` varchar(32) NOT NULL default '',
`Notes` text,
`UserKey` int(11) NOT NULL auto_increment,
`UserPKey` int(11) NOT NULL default 0,
`Phone` varchar(20) default NULL,
`RState` char(1) default 'L',
`Title` varchar(64) NOT NULL default '',
`Category` char(1) default 'I',
`WhenCreated` datetime default NULL,
`WhenModified` datetime default NULL,
`WhoCreated` varchar(50) default NULL,
`WhoModified` varchar(50) default NULL,
PRIMARY KEY (`UserKey`),
UNIQUE KEY `Id` (`Id`),
KEY `Name` (`FName`,`LName`),
KEY `Title` (`Title`)
);

I have added 40 rows in the table.
Some of the rows contains a space for FName and Title.

When I run the following query:

Select * from User order by FName limit 0,10;

It gives me the following error:
Got error 124 from storage engine


When I run the following query:

Select * from User order by FName limit 0,40;

It works fine.

The version of MySQL which I am using is 5.x.

Please reply ASAP.

Regards,
PS