Samba between Ubuntu server 10.10 and Windows Vista, Windows 7

I have a linux box running Linux server ubuntu 10.10. I have installed Samba on this linux box and want to share files with my laptops which run Windows Vista home and Windows 7 home. I have been struggling with the setup for almost a month but couldn't get it right. If I try to access share folder from Windows Vista, I get message

"Windows cannot access \\server_ip_address". 
Error code: 0x80070035. The network path was not found.

If I access from Windows 7, then after entering password to login I can see the list of share folders on Linux box. But if I click on a share folder, I get the same error message as above.

Tail /var/log/samba/log.windows7-pc I got the following message:

[2011/03/16 00:17:41.427238,  0] smbd/service.c:988(make_connection_snum)
canonicalize_connect_path failed for service sharemedia, path /root/sharemedia

Here is my setting in smb.conf [global] share modes = yes netbios name = Samba

workgroup = WORKGROUP

wins support = yes

encrypt passwords = true

[sharemedia]
comment = Tesing sharing using Samba
path=/root/sharemedia/
public = yes
valid users = samba_usr_name

; make sure all files are sensible permissions
create mask = 0660
force create mask = 0660
directory mask = 2770
force directory mask = 2770
directory security mask = 0000

; Normal share parameters          
read only = no
browseable = yes
writable = yes                     
guest ok = no

I resolved my problem connecting my Windows 7 box to my Ubuntu samba (11.10). I Had the "Windows cannot access" error (0x80070035 - the network path was not found" when trying to access the server (or share). I tried a lot of things, but when it came down to what actually solved it (all other items reversed) it was the "Microsoft Network client: Digitally sign communications (always)" setting that was causing my problem. Once it was disabled, I could see the shares and map the drive.