Lanman should be above the IP not below. (As I said above, it goes in order as below)
In regards to the underscore, Darrent meant it for the virtual host name, not the actual resource name.
As seen from your log snippet, I can see that you are using "Sharename_xxxx" for your virtual name.
Try something without an underscore as underscore is not a legal character for a hostname.
If it still doesn't probe, maybe you can take a screenshot of the properties view of your lanman resource?
(the section where you typed in the virtual hostname and Ip resource name etc to see how it's configured)
Please check whether your types.cf got properly updated or not, you can compare the current file with the backup taken by VCS during installation (in the dir C:\Documents and Settings\All Users\Application Data\Veritas\cluster server\vpibackup )
Your problem can cause if 5.0 types.cf file is not replaced by the 5.1 types.cf file, because Symantec changes only few agent types in each upgrade and it could be LANMAN for your bad luck !! :)