Strange thing is that non of the links in “available software sites” work in “install new software” section. Probably there is some thing wrong with eclipse software update.
The correct update site to use in Eclipse is http://vaadin.com/eclipse
This will probably try to look for a bunch of files, some which exist, some that don’t (e.g. contents.xml). If you get a connection time out it sounds like you could experience some network issues Especially if no other software sites work either.