well dont get too frustrated, as i have had this happen a few times myself, and usually it comes when installing a different build, or for that matter, another fresh install of one pc that was on the original HG while the other pc (laptop) was still connected and booted up. TBH, i dont know exactly why, i think something in the windows framework of the still joined HG pc, doesnt "let go" of the HG pc table. I noticed this when i was first installing RC on desktop, while having the laptop running with the 7000 beta. There was all kinds of wierd stuff going on there with the HG... showing the UserName then "()" without parenthesis. Was able to view the RC desktop from beta laptop, and navigate among the desktop shares, but nothing on HG, while i had setup the HG with my same share, enabled on all 6 accounts on this PC also sharing their files. Even the "microsoft" folder from the public shares wasnt showing up, so i know i had somekind of problem. But nevertheless, i just formatted the laptop and installed RC. Later on i found a somewhat similar problem with the HG library not showing contents, but the UserName and PC name now correctly showed. I had to right click properties inside the HG shared library and then go to "optomize folder for.." and another time that didnt work so reset to defaults then worked, thankfully.
So given all the quirkyness that i have seen, i know its not uncommon for this problem.
Best advice i can give is like i think i stated while back...leave any and all homegroups, completely, meaning you have to redo your HG library shares and added to library folder locations (i think), then to shutdown all pcs, 5min, along with the router, unplugged, go get something to drink or whatever. Come back and boot up just the desktop, only, after you login to desktop, then fire up router, wait a few minutes (atleast 30 secs +), go back to the desktop, create homegroup... fireup laptop, then hopefully you can then join with no problem.
