I had a similar experience switching from XP Pro 32-Bit to Vista Business x64. My MacBook and PC used the same username and password for authenticating so writing to network shares on my PC running XP worked like a charm.

I did a clean install to Vista Business, remapped all my shares, rebuilt drive level permissions on my data volume (Admins - Full, Users - Read) and made my user a member of the Admins group - Same as XP. For the life of me my MacBook could read from the Windows shares just fine, but I couldn't write to them. I tried adjusting Share level permissions, reapplying drive level permissions, no change.

On a hunch - I created a new user group on my PC - OtherAdmins, added my user to OtherAdmins and granted full permissions to OtherAdmins on my data volume - Immediately after that I could write to my network shares.

I would not be surprised if it's somehow tied into the UAC. Since you have to elevate yourself to Admin on the local machine, it may not grant actual Admin rights to a share, regardless of what user group you are in. Does it make sense that adding me to another group with the same permissions should work while another doesn't? No. Am I surprised by something like this? No.

I've been generally happy with Vista Business x64 - That's not to say it doesn't have it's quirks. All systems do. Most of the issues that I've had stem from having a small fault in my motherboard, which I can't afford to replace at the moment. So I live with frequent network disconnects and system boot lockups.

Not to should like a total jerk, but the first couple to share a bed on TV was Mary Kay and Johnny Which aired on CBS from 1947 to 1949