Durgaprasad Gorti's WebLog : Only one usage of each socket address (protocol/network address/port) is normally permitted
In working with a customer we ran into this issue from MOSS Content Deployment. This is a good one to keep in your back pocket if you disable file compression as Stefan discusses in his blog entry.
http://msdn.microsoft.com/en-us/library/aa560610.aspx
Durgaprasad Gorti's WebLog : Only one usage of each socket address (protocol/network address/port) is normally permitted