There's a few things that can be wrong, and it usually results in that lovely, generic and thoroughly unhelpful error message.
I found this thread really helpful
Post #2 here explained a firewall problem I was having http://ubuntuforums.org/showthread.p...horized+access
I also added "smb ports = 139" to to an annoying error in one of my logs based on the advice here http://kbase.redhat.com/faq/docs/DOC...7B7C7.ab46478d
If you look at my posts here http://ubuntuforums.org/showthread.php?t=1134928 you'll see what I had to do to get Samba fully working again in Jaunty.
I am no expert, but here goes (most of this is the first post in my own words, with some extras):
First thing, switch off any firewalls (Windows too). (You can bring them back on later, when you do, make sure that the correct ports are open [137, 138 TCP; 189 and 445 UDP]. See the post I mentioned above about the firewall as well.)
Now try the share again. If it works, you know it's a firewall messing things up and your Samba configuration is fine.
Next is to configure Samba and this is pretty easy, it's just matter of taking it one step at a time (the first post walks you through this). My smb.conf looks like this (and this works with Windows):
I've skipped a lot out as I had them just at default, you should be able to leave them too.
workgroup = WORKGROUP
security = user
username map = /etc/samba/smbusers
smb ports = 139
#An example share
path = /home/monkey/Pictures
valid users = samba_username
writeable = yes
Now, I am using "user" security, so I had to set up a Samba (network) user and map that to a Linux user. You can use other security settings and possibly ignore this.
Create the Samba user.
Now associate that Samba user with an Ubuntu user account.
sudo smbpasswd -L -a samba_username
sudo smbpasswd -L -e samba_username
Add an entry like this (you can add as many as you need):
sudo gedit /etc/samba/smbusers
Save the file.
ubuntu_username = samba_username
Now restart Samba
A lot of the above you can do using the GUI tool and you might find that easier. You need to install "system-config-samba" and it can be found under System/Administration/Samba once installed.
sudo /ect/init.d/samba restart
When Samba comes back up, give it a minute or two and try the shares again. If you get any problems, check the logs in "/var/logs/samba", they will probably show you what's wrong.
The command "testparm" is good for checking "smb.conf" and "smbtree" is a simple way of checking what Samba really sees without having to use Nautilus or similar.
If you use a firewall in Ubuntu; well, more correctly, if you use an iptools configuration utility - I found that Firestarter was pretty good. Watching for events in it can be a big help.