lophie, the bug is being worked on. However it's not trivial to fix. If you think it is, we are happy to accept patches though. Please don't spam our bug reports with such negative comments.
Thanks everyone else who provided information about your proxy configurations. We have a good set of information about what methods to support to start, and whwere to go from there, and are working on it. Please be patient as we get the fixes implemented in our many projects, and work to get the support shipped out to you. It may not work for all of you to start, but we will continue to work on adding support for some of the more complex configurations, after getting the majority supported at first. Thanks again, and we're sorry you haven't been able to use Ubuntu One behind your proxies.