Escape characters in XML msg from WM to Siebel

Hi

I’m currently sending messages from the XML adapter of webmethods to a business process running on the siebel web engine (through IIS).
When there is an escape character in the XML, for instance: & the xml that comes in on Siebel is cut short. For instance I sent:
beer & wine

Siebel receives:
beer

Has anyone an idea of why this is and how this can be solved?

Architecture:
WM enterprise 5.0.1 running on Solaris, XML adapter 4.2 on windows NT4 and Siebel 6.4 on the same NT machine as the adapter.

kind regards
Jeroen