Make sure that IPv6 is enabled. In services make sure that all the three peer networking services are started.
Yes it is strange that it worked before and not now.
Somtimes it helps to create the Homegroup on a different machine and join from the other but it sounds like you tried that. You may need to uninstall Kapersky also.
Try the link below which is a Homegroup trouble shooting walkthrough. The parts about switching between Public and Homegroup sharing can fix certain problems. http://technet.microsoft.com/en-us/l...16(WS.10).aspx
Homegroup check list>http://www.computerperformance.co.uk..._homegroup.htm Also try this because it fixed this same problem for someone else. I had a similar problem. My 64-bit desktop wired into the network and my 32-bit laptop wirelessly connected, stopped recognising one another on the homegroup. Recreating the homegroup and rebooting didn't help. Then, when I clicked "See full map" in the Network and Sharing Center, I discovered that even though I had set up my network as a Home network and it was displayed as such in the Network and Sharing Center, for some reason Windows 7 didn't "see" that. It wouldn't display the network map because it said I was on a Public network. So, I changed my network to a Work network, then back to a Home network, and the homegroup started working again. I had deleted the homegroup on the laptop prior to making these changes, so I simply rejoined and everything's now working again.
So make sure you aren't mistakingly on a Public network because Homegroups won't work from there.