The 5.1 beta will most likely be posted here on Monday (i.e. tomorrow).
It will contain only some of the new stuff I was talking about - with the rest being included in the v6 beta that will follow in about 1 month. At least that's the plan for now.
BTW yes, the 5.1.677 package is a red herring - that is, it's identical to the original 5.0.677 with the new virus defs bundled with it. It's not the real v5.1.
Thanks
Vlk