I think my problem is similar: I connect to a NAS (Western Digital Mybookworld, where I opened a ssh channel, so I can control linux box there - with basic linux and samba) from Windows 7.
Usually I choose its name (\\mybookworld) in explorer and it connects without asking any password.
After 4-5 minutes of inactivity Windows can't access anymore the linux box and seems to me an authentication problem, since other pcs in the network continue to communicate with my nas. If some program was connected, it crashes and it's impossible to kill the process from task manager.
Then I try to put IP address of my NAS it reconnects for some time, then the same.
I must reboot everytime, but due to hanging programs windows does not reboot. I have always to switch power off brutally.
I tried to remove credentials, to activate/deactivate ntlmv2 and ntlm and lm authentication via registry (windows 7 home premium has no gui for that, you must pay some fee more to have a fully functional system?)
I tried to shut down every firewall
I don't want to reinstall Windows XP. Anybody there can hel us?