Regarding an older post, I finally managed to solve both problems. In case anyone else runs into them:

The Samba Problem: ports! The following ports need to be opened on the Linux box for trouble-free sharing with Windows:

• 137:udp (AKA netbios-ns)
• 138:udp (AKA netbios-dgm)
• 139:tcp (AKA netbios-ssn)
• 445:tcp (AKA microsoft-ds)

The Sharing Tab Problem: registry! As per an answer the the ExpertSexChange site (which you can't read unless you pony up some cash), my registry had been edited to disable it (probably by one of those tweak registry programs I sometimes foolishly play with). To repair I had to recreate the following entry:

[HKEY_CLASSES_ROOT\Folder\shellex\ContextMenuHandlers\Sharing]
“(default)”="{f81e9010-6ea4-11ce-a7ff-00aa003ca9f6}“

and edit another to move the value in the ”~~disabled~~“ key back into ”(default)“:

[HKEY_CLASSES_ROOT\CLSID\
 {f81e9010-6ea4-11ce-a7ff-00aa003ca9f6}\InProcServer32]
”(Default)"="ntshrui.dll“
”~~Disabled~~"="ntshrui.dll“
”ThreadingModel"="Apartment"