I am sorry that you have downloading issues. Unfortunately I can see that too today and the reason is Sourceforge.net service. They were hacked and due some reason from recovering from the attack, all new uploads on Thursday/Friday/weekend have these issues as far as I know :-(.
Look at http://sourceforge.net/blog/sourceforge-attack-full-report/. They don't have any ETA for fixing the issue now.
Try to download Seam with wget or any other download manager, which can resuming download.
Anyway in the meantime I have uploaded the release at download.jboss.org:
Ahh, the goodness of Seam returns :0)
Thank you kindly for the post Marek, most helpful indeed.
All the best, Andrew