For sometime I’ve had problems connecting from my Vista laptop to my MacBook Pro.  I’ve only been  able  to connect  the other way.  Finally a solution.

This thread recommends the following:

On the start menu in the search field type “gpedit.msc”, hit enter. This will open the group policy editor.

Go to “Computer Configruation” –> “Windows Settings” –> “Security Settings” –> “Local Policies” –> “Security Options”

In the pane on the right side of the screen, select “Network Security: LAN Manager Authentication level.” By default this read “Send NTLMv2 response only.”
Change “Send NTLMv2 respone only” to “Send LM & NTLM — use NTLMv2 session security if negotiated”

restart the client

If you use a famillial vista try this.  You must modify the BDR

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
DWORD named : LmCompatibilityLevel must set to 1