SMBFS is rock solid here...
OS4 can sometimes become unstable if you've installed older programs on it.
Do a "list libs:" in the cli and look at the dates of the files in there. Compare any dated later than when you installed OS4 with the libs directory on the OS4 CD. If you see any in both, replace yours with the CD copy. An installer for an old piece of software might have downgraded something...
