I have a server running the TKL File Server atop a Proxmox virtual environment (along with another appliance), and it all went fine for some months -- I was able to use it happily as a backup server for a Win 7 Pro workstation.
Now the W7P machine can't see the server anymore, while everything else looks fine: the server is up and running, accessible by HTTP, etc.: just the Samba services are unreachable.
Note: I have had a similar problem before, with other boxes as well; tipically, from what I discovered, troubles can arise when the time zone of the server is different from that of the W7P client. Sometimes you can be fooled by the same time, but a different DST/no-DST setting, some others just a difference of a few minutes can make the server unreachable (encrypted communication requirements?).
In this case, time zone and time are the same, so it doesn't look to be that kind of problem... any suggestion?