Some folks have reported problems logging into RubyForge from networks behind certain ISPs' not-so-transparent proxies - Telkom and TPG users seem to have this problem, and folks in Singapore have reported it as well. So there's been a long-standing bug on this problem.
I think we've got a work around for this now since I've hacked some IP subnet exclusions into the session tracking code. It seems to be working; thanks to Sau Sheong Chang and Andy Shen for helping to test out the fix.
So anyhow, I'm closing that bug. If you have problems logging into the RubyForge site and keep getting cookie-related errors, please drop me a note and we'll sort through it. Thanks!