Failed to get the ItemType with ID undefined

Am trying to approve some tasks in my inbasket. But i couldn't view a proper work item in the grid. I can see some junk numbers as work item and on click of that i get the error as 

"Failed to get the ItemType with ID undefined"

below is the complete error detail ,

-<SOAP-ENV:Envelope>
-<SOAP-ENV:Body>
-<SOAP-ENV:Fault>
  < faultcode > SOAP-ENV:Server.ItemTypeNotFoundException </ faultcode >
  < faultstring > Failed to get the ItemType with ID undefined. </ faultstring >
-<detail>
  < af:legacy_detail > Failed to get the ItemType with ID undefined. </ af:legacy_detail >
  < af:exception message =" Failed to get the ItemType with ID undefined. " type =" Aras.Server.Core.ItemTypeNotFoundException " />
 </detail>
 </SOAP-ENV:Fault>
 </SOAP-ENV:Body>
 </SOAP-ENV:Envelope>
Why work item is showing a junk value? how to resolve this issue.
Actually this work item is already submitted to a workflow and it is under some state.
Am very new to Aras/Plm programming and looking forward for some help asap.
Thanks.
Bala.