Yeah, they changed the Beta download area when they updated to the Beta 2. They have it set up with a installer manager program to download and install the program. This only works for the 32 bit Vista for now. If you do not already have Beta 1 installed before Beta 2, then we 64 bit users are left out in the cold until they release a 64 bit version.
The only option for now it to download the non Beta release 8.1.0178
Version of WLM and install and use it, and check every so often for a 64 bit update.
Hope this helps,