Intermittent SSLHandshakeException in Adinsight API

Hi,

We are getting the following exception while calling Adinsight API from bing Ads SOAP API from java code.

Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

    at org.apache.axis.AxisFault.makeFault(AxisFault.java:101)

    at org.apache.axis.transport.http.HTTPSender.invoke(HTTPSender.java:154)

    at org.apache.axis.strategies.InvocationStrategy.visit(InvocationStrategy.java:32)

    at org.apache.axis.SimpleChain.doVisiting(SimpleChain.java:118)

    at org.apache.axis.SimpleChain.invoke(SimpleChain.java:83)

    at org.apache.axis.client.AxisClient.invoke(AxisClient.java:165)

    at org.apache.axis.client.Call.invokeEngine(Call.java:2784)

    at org.apache.axis.client.Call.invoke(Call.java:2767)

    at org.apache.axis.client.Call.invoke(Call.java:2443)

    at org.apache.axis.client.Call.invoke(Call.java:2366)

    at org.apache.axis.client.Call.invoke(Call.java:1812)

When we call this API from a some other server, it works for some time and then exception starts coming again. And if we don't stop the calls then, it looks like the server gets blacklisted at MSN end. Please help to resolve the issue. We didn't change anything recently in the code and it was working till last week on bing Ads version 13.