I'm not sure what you are using for yr web services.
If you are using Jboss-net.sar which is wrapper to Apache-AXIS then I dont see why can't you use .NET client.
The reason I say that beacuse, I haven't used jboss-net.sar because of its portability issues . But I have used Apache -AXIS1.1 very heavily integrating it in Jboss-3.2.1 and invoked web services useing asp.Net client, VB.net Client, Perl client (using SOAP::Lite) and of course java clients.
Conclusion if you use APACHE-AXIS with Jboss, then no issues with .NET and On that I would say if you use jboss-nat.sar shouldn't be an issue.
Soon I will be publishing a chapter on this in addition to the already available chapters.