Two Ubuntu 16.04 systems, one has been running about two years now. Just today I created another Ubuntu 16.04 system first from a recently burned DVD install disk then updated with several packages I know I need as well as running the updater.
The new system hangs on mount commands to XP shares, example: mount -t cifs -o user=guest,passwd=,rw,iocharset=utf8,file_mode=0777,dir_mode=0777,noperm //toller/z /media/z
The other XP system handles the mount command just fine
The new system does not hand if a similar mount is directed to a share on a Ubuntu system
XP systems can mount a share that exists on the new Ubuntu system
Filewall makes no difference a) disabling it - no change and b) identical rules to the two year old Ubuntu system
XP has a limit on the number who can access a share - not an issue - did a umount on the working system then new system gives same hang then old system mounts some thing again.
It's as if there is some small step or package which was not done on the new Ubuntu 16 system.
Terrance answered the question. It is now necessary to add the vers=1.0 parameter to the mount command if the target of the mount is an XP system. The revised command is as follows: mount -t cifs -o user=guest,passwd=,rw,iocharset=utf8,file_mode=0777,dir_mode=0777,noperm,vers=1.0 //toller/z /media/z