Error Code 4600

Error Code 4600

<string xmlns="ZohoCRM">
<?xml version="1.0" encoding="UTF-8" ?> <response uri="/crm/private/xml/Leads/insertRecords"><error><code>4600</code><message>Unable to process your request. Please verify if the name and value is appropriate for the "xmlData" parameter.</message></error></response>
</string

getting above response when i try to request through webrequest(c#)
and if i pass same xmldata through url in browser it works fine.