Easy Solution - Try catching Soap Exception instead of Generic .net Exception and see InnerXML message and it shows CRM code: 0x80040217 with description like: "Missing field/attribute" or it just says plain "Platform".
- If you are doing an insert check that all fields that you are using in the query/fetchXML are not misspelled.
- If you are doing an Update or delete check the above and ensure GUID you are using does exist in CRM database.
That should be the catch! Write to me if that does not solve your problem. Thanks - Dipesh