Actually, I thought the same thing....
...and, it may well be the problem in the end. But the permissions on the executable are 'rwxr-xr-x', and it launches fine in the other profiles.
The exact command is.....
'kfmclient openProfile webbrowsing'
When the command is....
'kfmclient openProfile filemanagement'
....it works fine.
However, I think you are on the right track, and I will look further at permissions. Thanks for the pointers.