If you have several people in your RubyForge project you may have hit this problem - when one person uploads files to the project's virtual host, the files get written with non-group-writeable permissions, and so when someone else tries to upload files it fails with an error. Boooo. Well, there's a fix in place, or at least a workaround, and it's documented in the RubyForge FAQ - see # 25. Or just see this screenshot and you'll get the gist of it. The nice thing is that PostgreSQL seems to be fast enough - or the groups table only few enough records - that I've scheduled that cronjob to check for the setting once a minute and it doesn't seem to be impacting things at all. Good times.
As long as I'm writing, if you've got a RubyForge project, please scan this list of tips for keeping your project tidy.
And I just noticed that RubyForge just went over the 4000 project mark. Very cool!