There is also a local security policy in Windows XP which MAY or MAY NOT need to be set. I recall setting it in the past, but do not know if it's still relevant. I is the packet signing policy, and I found the info from the Samba page. I can't give you any better than that right now.
I have also found that connectivity comes and goes, mostly seeming to be related to load cause by Windows' SMB stack.
Best I got for ya here. I know that after moving from the WarpEngine 4040 to the CyberStorm MKIII 060 has made a LOT of difference in Samba stability.
