So I have been working sith Sam Shillace over at Writely, a very cool product if no one has seen it, on problems they have been having posting against SOAP::Lite servers. Writely is one of the only successful "Web 2.0 Applications" built on top of .NET I have seen - so kudos to his and his team for proving so many people wrong that smokin' cool apps can be built on top of .NET.
Anyway that little fact is relevant because .NET has implemented a little known HTTP Header called "Expect" (officially part of the HTTP 1.1 spec) which SOAP::Lite does not support... yet.
However, I think I may have fixed that problem. I have checked in a change to HTTP.pm that I believe will do just that. It still needs to be tested, but I am keeping my fingers crossed. For you bleeding edge folks, you can check out the source code from CVS.