Because I had hangs on Ubuntu with smbfs mounted drivers (the new 1.5TB WorldBook and my USB2 drive from the laptop) I Googled around for some solutions. One thing that I noticed is that most newer forum posts tell you to mount the drives as type “cifs” instead of “smbfs”. Most of the time I can reproduce a “hang” when going to a directory on my WorldBook and clicking on it (in the filebrowser) so that it would start to generate tiny icons of the pictures inside the directory. After having done one icon, the system would freeze until I killed the filebrowser and after a while I unmounted and remounted the drive.
The hang does not occur when mounting the drive as type cifs. The mounting process itself seems (did no accurate testing) faster too. I’ll let you know if this solves the problem completely.
BTW cifs is the successor to smbfs, but it is said that it cannot handle shares from Windows 95 and Windows 98, but that’s not a real problem for most people. Cifs is more actively maintained as well, so bugfixes and security patches are likely to find its way faster to cifs than to smbfs.