Please try the following on your Vista computer:
- Click Start
- Click Control Panel
- Click System and Maintenance
- Click Administrative Tools
- Double-Click Local Security Policy
- In the left pane, click the triangle next to Local Policy
- In the left pane, click Security Options
- In the right pane near the bottom, double-click "Network security: LAN
manager authentication level"
- Click the drop-down box, and click "Send LM & NTLM - use NTLMv2 session
security if negotiated"
- Click OK
- Restart the computer
Windows Vista Support Faq