After a few problems getting vista to see shared network drives on some network attached devices (and sometime on XP shared drives as well), I finally found the solution:
Start -> secpol.msc (in the Search field).
In the left pane: Local Policies -> Security Options. In the right pane: double click on: “Network security: LAN Manager authentication level”.
Local Security Setting tab -> “Send LM & NTLM – use NTLMv2 session security if negotiated” option. -> OK.
Seems like microsoft have used Vista to cut ties with the past (insecure) versions of network share authentication. Of course they failed to realise that network attached drives cannot be easily updated.