Since you already tried using CVS maybe you would also like to try a first experimental implementation of a download write buffer.
We switched to SVN recently so you need to use SVN to get the branch sources located at:
Code:
http://svn.sourceforge.net:443/svnroot/phex/phex/branches/download-rework-branch
The modifications are very new and were quite heavy so be aware of possible errors/crashes/corruptions.
Gregor