The uploadprogress extension for PHP never really worked on Windows and since I don't have a Windows development environment I could never do a proper analysis of the problem. Until this week, when Tomas Holusa sent me an email telling me about some VCWD_RENAME problems on Windows.

A patch that was submitted a while back confirmed the issue and a new patch was written and submitted to take care of the problem. You can try out the new extension on Windows with either the normal Wind32 build or Win32 nts build.