I was able to do API calls with partner.wsdl.  However, i am no longer able to do so and get the following error message:

com.sforce.ws.ConnectionException: Failed to parse detail:  START_TAG seen ...</sf:exceptionMessage><sf:upgradeURL>... @1:752 due to: com.sforce.ws.ConnectionException: unable to find end tag at:  START_TAG seen ...</sf:exceptionMessage><sf:upgradeURL>... @1:752
    at com.sforce.ws.transport.SoapConnection.parseDetail(SoapConnection.java:238)
    at com.sforce.ws.transport.SoapConnection.createException(SoapConnection.java:204)
    at com.sforce.ws.transport.SoapConnection.receive(SoapConnection.java:150)
    at com.sforce.ws.transport.SoapConnection.send(SoapConnection.java:99)
    at com.sforce.soap.partner.PartnerConnection.login(PartnerConnection.java:790)
    at com.sforce.soap.partner.PartnerConnection.<init>(PartnerConnection.java:406)
    at com.sforce.soap.partner.Connector.newConnection(Connector.java:27)

According to the login history, each call was actually log in successfully.  Any suggestion to resolve the issue?  Thanks!