have you checked the ip address to see if they are in the same block??
I was looking at the code for banning and I banned a test account and I'm gonna have to remove the cookie to login as admin again

you cant stay logged in once you click any link your
"disabled".
if you don't ban folks and you need something temporary
you could change the text:
$txt[430] = ', Your account has been disabled. Please contact the forum administrator for further assistance';
banning is quite effective what level of disablement do you mean.
You could create another entry in the banned table and make type=disabled value=$username
Then do a query in banned() to display a custom message if the user is disabled but it's the same thing
Aquilo