I have a multisite install with about 40 blogs. All blogs but one (id=5) works fine.
In this one blog, when trying to access the users list it shows an empty list (header & footer) with the text 6 items below the list footer.
When trying to create a new user on this blog I can see that the roles dropdowns are empty (thus not allowing to create a new user).
Had the same problem.
The issue was in wp_options table.
Find line where option name is wp_user_roles and look what’s going on there. This line is responsible for user roles, and if they are an a mess, users canot be shown as well.
Better copy option_value from the other table.
(Change wp_ to your prefix).
Without access to your Database or Code it’s really hard to give you something like a useful solution.
But here go some possibilities:
If both of these doesn’t work, try checking for the wp_5_options on this blog, I thing it might be a problem with the row with this “option_name” wp_5_user_roles, go to a working blog and copy the contents of this option and past on this one. Don’t forget to backup.
Hope I could help on something.