We're receiving the following error when making a webservice callout:

16:05:08 ERROR - Evaluation error: System.CalloutException: IO Exception: DerInputStream.getLength(): lengthTag=75, too big.
16:05:08 ERROR - Evaluation error: Class.wsFiberlinkCom.EspWebServiceImpl.checkIfValidMaas360UserName: line 58, column 13
AnonymousBlock: line 4, column 1

Any idea what the source is?

Thanks in advance.