I ran into something similiar so I did the following and it seemed to work for me.
Created a share on my XP box with read & write permissions
then I created a linux mount point in my /usr/local/ by doing the following:
mount -t smbfs -o workgroup=<workgroup name>,username=<username>,password=<password> //<SERVERNAME>/<SHARE NAME> /usr/local/samba_share
Now you just replace the <....> with your information, make sure you do not have spaces. That should allow you to connect to your XP box.
I hope this helps.