QBWC1012: Authentication failed due to following error message. Client found response content type of 'text/xml', but expected 'text/xml'

20150604.02:34:43 UTC   : QBWebConnector.WebServiceManager.DoUpdateSelected() : updateWS() for application = 'APPNAME' has STARTED
20150604.02:34:43 UTC   : QBWebConnector.RegistryManager.getUpdateLock() : HKEY_CURRENT_USER\Software\Intuit\QBWebConnector\UpdateLock = FALSE
20150604.02:34:43 UTC   : QBWebConnector.RegistryManager.setUpdateLock() : HKEY_CURRENT_USER\Software\Intuit\QBWebConnector\UpdateLock has been set to True
20150604.02:34:43 UTC   : QBWebConnector.RegistryManager.setUpdateLock() : ********************* Update session locked *********************
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.instantiateWebService() : Initiated connection to the following application.
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.instantiateWebService() : AppName: APPNAME
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.instantiateWebService() : AppUniqueName (if available): APPNAME
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.instantiateWebService() : AppURL: http://localhost/quickbooks/qbwc/qbwc.php
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.do_serverVersion() : *** Calling serverVersion().
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.do_serverVersion() : Actual error received from web service for serverVersion call: <Client found response content type of 'text/xml', but expected 'text/xml'.
The request failed with an empty response.>. For backward compatibility of all webservers, QBWC will catch all errors under app-not-supporting-serverVersion.
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.do_serverVersion() : This application does not contain support for serverVersion. Allowing update operation for backward compatibility.
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.do_clientVersion() : *** Calling clientVersion() with following parameter:<productVersion="2.1.0.30">
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.updateWS() : Actual error received from web service for clientVersion call: <Client found response content type of 'text/xml', but expected 'text/xml'.
The request failed with an empty response.>. For backward compatibility of all webservers, QBWC will catch all errors under app-not-supporting-clientVersion.
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.do_clientVersion() : This application does not contain support for clientVersion. Allowing update operation for backward compatibility.
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.do_authenticate() : Authenticating to application 'APPNAME', username = 'Admin'
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.do_authenticate() : *** Calling authenticate() with following parameters:<userName="Admin"><password=<MaskedForSecurity>
20150604.02:34:43 UTC   : QBWebConnector.SOAPWebService.do_authenticate() : QBWC1012: Authentication failed due to following error message.
Client found response content type of 'text/xml', but expected 'text/xml'.
The request failed with an empty response.
More info:
StackTrace =    at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
   at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
   at QBWebConnector.localhost.WCWebServiceDoc.authenticate(String strUserName, String strPassword)
   at QBWebConnector.localhost.WCWebService.authenticate(String strUserName, String strPassword)
   at QBWebConnector.SOAPWebService.authenticate(String UserName, String Password)
   at QBWebConnector.WebService.do_authenticate(String& ticket, String& companyFileName)
Source = System.Web.Services
20150604.02:34:43 UTC   : QBWebConnector.RegistryManager.setUpdateLock() : HKEY_CURRENT_USER\Software\Intuit\QBWebConnector\UpdateLock has been set to False
20150604.02:34:43 UTC   : QBWebConnector.RegistryManager.setUpdateLock() : ********************* Update session unlocked *********************
20150604.02:34:43 UTC   : QBWebConnector.WebServiceManager.DoUpdateSelected() : Update completed with errors. See log (QWClog.txt) for details.

I've triple checked that the .qwc username is the same as it is in the quickbooks_user table and the password given in the connector matches as well. The error message claims it's getting what is expected. Any help on where to go from here?