[Fiddler] ReadResponse() failed: The server did not return a response for this request.

Hii
In implementing the REST service when I run the URL then I get the following error..
"[Fiddler] ReadResponse() failed: The server did not return a response for this request."I want to return the response in JSON format ?However when I check for returning the response in XML format then its working absolutely perfect...What could be the possible cause of this when I return JSON response?
This is my XML response:
 

<CompanyList>
<Company>
<Action i:nil="true"/>
<CreatedDateTime>0001-01-01T00:00:00</CreatedDateTime>
<CreatedUser>00000000-0000-0000-0000-000000000000</CreatedUser>
<LastUpdatedDateTime>0001-01-01T00:00:00</LastUpdatedDateTime>
<LastUpdatedUser>00000000-0000-0000-0000-000000000000</LastUpdatedUser>
<VerificationPassword i:nil="true"/>
<Version>0</Version>
<Address i:nil="true"/>
<AddressId>00000000-0000-0000-0000-000000000000</AddressId>
<Id>b9ca2e32-ce88-4d72-99ce-9bc592511e85</Id>
<ParentCompanyId>00000000-0000-0000-0000-000000000000</ParentCompanyId>
<Phone i:nil="true"/>
<ProviderCompanyLookup i:nil="true"/>
</CompanyList>

 
In the above response is default i.e returning null.I have gone through Google that one of the problem can be a DateTime issue.So have to set it to a bigger value..But couldn't understand where to set and how to set ?
 
If this is not my problem then what could be the problem?
 
Any help is appreciated....
 
Thanks..