The Best fix for Network Shares
The biggest problem that I've seen with Vista file sharing, ie: connecting to shares, is that Vista only uses NTLMv2 by default. The best fix is to fire up "GPEDIT.MSC", and navigate to:
Computer Configuration>Windows Settings>Security Settings>Local Policies>Security Options
Then on the right side, scroll down to "Network security: LAN Manager authentication level", and change "NTLMv2" to just "NTLM".
I don't like to use the host sharing, I prefer Samba. This has fixed all previous connection issues I have had in the past.