Web Service Error

Hi,

I am creating a web service and I keep running into this error:

{

   "error" : {

     "code" : "005056A509B11EE1BB8AF4A65EC3CA20",

     "message" : {

       "lang" : "en",

       "value" : "Invalid parametertype used at function '' (Position: 13)"

     },

     "innererror" : {

       "transactionid" : "54B08B93AF393071E1000000821D9460",

       "timestamp" : "20150114185933.2547720",

       "Error_Resolution" : {

         "SAP_Transaction" : "Run transaction /IWFND/ERROR_LOG on SAP NW Gateway hub system and search for entries with the timestamp above for more details",

         "SAP_Note" : "See SAP Note 1797736 for error analysis (https://service.sap.com/sap/support/notes/1797736)"

       }

     }

   }

}

I am passing a headerguid that may be the issue, and the header guid type has either been binary, guid, or string. None of these have worked. Is there a particular data type that needs to be passed in the url parameters?

Here is the url being used:

/sap/opu/odata/sap/ZFM_NOTES_SRV/EtTextsSet?$filter=(Headerguid EQ '001E0BFCBE6C1ED28E97B35228641503')&$format=json

Thanks.