Integrity Webservice via Powershell

Has anyone attempted webservices via powershell?

We're familiar with PTC Integrity webservices via soapui and java.

Powershell is proving a challenge.

Here's a code sample:

$mksws=New-WebServiceProxy-Uri"MYSERVER/webservices/10/2/Integrity/?wsdl"

$ns=$mksws.GetType().NameSpace

$pr=New-Object ($ns+".ProjectRequest")

$pr.transactionId ="?"

$pr.FieldList ="Name"

$pr.Username ="xxxxx"

$pr.Password ="xxxxx"

$pr.ImpersonatedUser =$null

$pr.DateFormat =$null

$pr.DateTimeFormat =$null

$gp=New-Object($ns+".getProjects")

$gp.arg0 =$pr

#$response=New-Object($ns+".getProjectsResponse")

$response = $mksws.getProjects($gp)

Returns this wrapped in html

PTC Integrity Server - Error report

  The server encountered an internal error () that prevented it from fulfilling this request.

Server log shows this

ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[localhost].[/webservices/10/2/Integrity].[Integrity_10_2]] Cannot find message associated with key standardWrapper.acknowledgeException
java.lang.IllegalArgumentException: You can only write using the application write buffer provided by the handler.
at org.apache.tomcat.util.net.SecureNioChannel.write(SecureNioChannel.java:381)
at org.apache.tomcat.util.net.NioBlockingSelector.write(NioBlockingSelector.java:53)

...