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Congrats on the post count firstly ;) Also I would be very careful when downloading bt from anywhere else. I'd go as far to say that the revisions aren't worth the downloads. I'm still using bt 4 final, I tried downloading r1 and gave up because they are stupidly slow downloads.
I wish I could tell you the release date for BT5, it was supposed to be early this year (making r2 pointless). However the bt 'roadmap' which detailed this release has been altered and doesn't show the release anymore. Possibly due to the security situation.
Roadmap: http://www.backtrack-linux.org/bt/roadmap/
This proves it was there (2nd to last para): http://www.backtrack-linux.org/tag/roadmap/
EDIT: Also I have the alfa and don't have any problem running bt4 final :)