A new libxml build is available http://www.ctindustries.net/patches/winphplibxml.zip
It has a back ported windows specific patch which fixes the simplexml tests.
iconv has also been bumped up to 1.9.1
the modified file is included in the zip for those building their own libxml. It is not need for the 2.6 branch, only for 2.5.11