It has been reported in the bugzilla for mandrakesoft a problem that
has been reduced to curl not being able to mix --disable-epsv for ftp
downloads and IPv6 addressing. If you have an IPv6 testbed, (unlike
myself:), you'll find the relevant information on how to reproduce the
bug here:

http://qa.mandrakesoft.com/show_bug.cgi?id=12285

I can help with additional info if you need it.

-- 
rgs