Error on Implicit conversion

Hey I have a problem to this query, yesterday function normaly, but we reboot the server and now send me this error message:

Msg 245, Level 16, State 1, Line 1
Conversion failed when converting the varchar value 'sdv' to data type int.

this is the query, i wish to know what happend.

SELECT ZKA.[CHECKTIME], ZKA.[SENSORID], ATT.[DESCRIPTION_EN], ATT.[LOCATION], ATT.[SUBTYPE], UI.[USERID], UI.[NAME], UI.[TITLE]  
FROM [att3000].[dbo].[CHECKINOUT] ZKA   
INNER JOIN [att3000].[dbo].[Universal_Devices] ATT 
ON ZKA.[SENSORID] = ATT.[FOREIGN_ID] 
INNER JOIN  [att3000].[dbo].[USERINFO] UI 
ON  ZKA.[USERID] = UI.[USERID] 
WHERE ZKA.[CHECKTIME] BETWEEN '2014-06-06 00:00:00.000' AND '2014-06-06 23:59:59.999' 
AND UI.[SSN] = 890  --
AND ATT.[SUBTYPE] <> 4 
ORDER BY ZKA.[CHECKTIME] ASC