I have a custom attribute field in my CPD which contains fully numeric and mixed text and numeric values, when searching for a numeric value (eg 12345) I get the error below, searching for a value beginning with a character works ok:

<h1>CDbException</h1>

CDbCommand failed to execute the SQL statement: SQLSTATE[22018]: [Microsoft][SQL Server Native Client 11.0][SQL Server]Conversion failed when converting the varchar value 'T00499' to data type int.. The SQL statement executed was: SELECT count(*) as cnt
FROM [participants] [p]
left join users luser ON luser.uid=p.owner_uid
LEFT JOIN participant_attribute attribute1 ON attribute1.participant_id=p.participant_id AND attribute1.attribute_id=1
LEFT JOIN participant_attribute attribute2 ON attribute2.participant_id=p.participant_id AND attribute2.attribute_id=2
LEFT JOIN participant_attribute attribute4 ON attribute4.participant_id=p.participant_id AND attribute4.attribute_id=4
WHERE (attribute4.value = :condition_0) (C:\limesurvey\framework\db\CDbCommand.php:528)

#0 C:\limesurvey\framework\db\CDbCommand.php(425): CDbCommand->queryInternal('fetchColumn', 0, Array)

#1 C:\limesurvey\application\models\Participants.php(259): CDbCommand->queryScalar()

#2 C:\limesurvey\application\controllers\admin\participantsaction.php(815): Participants->getParticipantsCount(Array, Object(CDbCriteria), NULL)

#3 C:\limesurvey\application\controllers\admin\participantsaction.php(782): participantsaction->getParticipants_json(Object(CDbCriteria))

#4 [internal function]: participantsaction->getParticipantsResults_json()

#5 C:\limesurvey\framework\web\actions\CAction.php(107): ReflectionMethod->invokeArgs(Object(participantsaction), Array)

#6 C:\limesurvey\application\core\Survey_Common_Action.php(100): CAction->runWithParamsInternal(Object(participantsaction), Object(ReflectionMethod), Array)

#7 C:\limesurvey\application\controllers\admin\participantsaction.php(51): Survey_Common_Action->runWithParams(Array)

#8 C:\limesurvey\framework\web\CController.php(309): participantsaction->runWithParams(Array)

#9 C:\limesurvey\framework\web\CController.php(287): CController->runAction(Object(participantsaction))

#10 C:\limesurvey\framework\web\CController.php(266): CController->runActionWithFilters(Object(participantsaction), Array)

#11 C:\limesurvey\application\controllers\AdminController.php(169): CController->run('participants')

#12 C:\limesurvey\framework\web\CWebApplication.php(276): AdminController->run('participants')

#13 C:\limesurvey\framework\web\CWebApplication.php(135): CWebApplication->runController('admin/participa...')

#14 C:\limesurvey\framework\base\CApplication.php(162): CWebApplication->processRequest()

#15 C:\limesurvey\index.php(178): CApplication->run()

#16 {main}