Tiger -> Win Xp Pro File Sharing Connectivity


I'm ready to toss my new Powerbook out of the window...

both Powerbook and XP machine are connected to router/DSL modem

both have DHCP assigned address and are on same subnet & workgroup name. Ping works between Mac and WinXP machine (both directions)

Identical user account / password combination exists on Mac and Win XP machine

Windows Sharing and SMB/CIFS enabled on Mac, File and Print Sharing enabled on Win XP Machine (simple file sharing disabled -> access control list for specified share with user name mentioned above added as full control)

All Mac -> Win XP connectivity in terms of SMB://<WinXPMachine>/share does NOT work <WinXPMachine> being either:
Computer name as in My Computer -> Properties
IP address
computer.lan (domain in router's DNS Server Configuration)

All Win XP -> Mac connectivity is NOT functional eigher:
- Mac invisible in workgroup or network places
- \\<max>\username does not work ("<mac> The network path was not found" after considerable delay)
<mac> being either IP or specified computer name in System Preferences -> Sharing...

I am totally at a loss here... scanned the internet for hours (including MacOSX.com's considerable list of hits with "Tiger" and "XP" in them, but nothing seems to get me going... There's a lot of helpful stuff inside Apple Developer Connection, but it's all just slightly different from my configuration or problem. I thought I had the golden egg with a hint on incompatible password encryption, to be mediated by setting a Group Policy record straight in WinXP, but all those apply to Windows2003 servers, while my XP computer is not a server...

Help would be sincerely appreciated!