Needing Urgent Help!

We are having some trouble with importing leads via API. It was working fine up until recently.

We are getting the following error...

<?xml version="1.0" encoding="UTF-8" ?> <response uri="/crm/private/xml/Leads/insertRecords"><error><code>4835</code><message>Unable to parse XML data</message></error></response>

Any Ideas?

Thanks.