The text/plain thing sounds like a problem -- make sure that the CGI is actually executing, and not just the file being returned.

I've run into a few problems when people tried consuming a SOAP::Lite service using a strictly typed language, and I had to do some work in making sure it serialized correctly -- I had a few items that were strings of numbers, and SOAP::Lite kept marking it as numbers -- I was using RPC/encoded SOAP, and not using SOAP::Data to declare what the values were, as I was getting them from another SOAP call. In the end, I replaced SOAP::Serializer to make sure it sent what I wanted.

I believe that issues of compatibility have come up in the past on the soaplite mailing list -- you might check their archives, but it's also possible that it's no longer an issue as they've moved away from the overhead of RPC/encoded messages.