After installing the new Eclipse 3.6M7 Stream Stable Build I could not connect to any update site nor to another project site.
After some investigation I found out that there must be something wrong with the used IP protocol stack. Eclipse seems to use IP4
So if you start eclipse with
./eclipse -vmargs -Djava.net.preferIPv4Stack=true
eclipse should be able to reach your update sites.
A small update to my Post:
I just found out that the real problem is a new sysctl-setting under /etc/sysctl.d/bindv6only.conf. LOL
Check the net.ipv6.bindv6only item this should be 0 (null).
After changing reset the sys kernel variabels with:
sudo invoke-rc.d procps restart