I had this problem too.. it seems that the optional perimeters are not so optional right now...
where... '!ban Minge' will not work right now...
'!ban Minge 0 "Being a retard"' will....
Don't know why.. but it does work..
therefore... the menu wont let you ban.. you can only do it from the console or from chat..
you'll need to pass all the perimeters. (including time and reason)
test this on someone and tell me if it works.. and hopefully They will find out why it's not working right soon and fix it =)
EDIT::::
I just tested it myself and it seems to be what I said..
Here are some error messages I picked up from console..
ulx ban bullet
20:14:46 SERVER: ULib/shared/misc.lua:103: attempt to index local 'str' (a nil value)L 10/07/2007
ulx ban bullet 1
20:15:00 SERVER: modules/util.lua:121: attempt to concatenate local 'reason' (a nil value)L 10/07/2007
ulx ban bullet 1 "whatever"
20:15:10 L 10/07/2007 - 19:11:12: "Bullet Delivery Service<3><STEAM_0:1:15873155><>" disconnected (reason "Kicked and banned")
20:15:10 (ADMIN) (Console) banned Bullet Delivery Service for 1 minute(s) (whatever)
So it works.. but only if you tell it EVERYTHING it wants to know. Personally I like this, because it forces my admins into using the reason perimeter! =)
EDIT 2...
Tried this on my Spacebuild server, and it too is experiencing a form of this bug.. by a form I mean.. It will let me do 'ulx ban <player> [time] and Leave out the reason.. where on my regular server, I have to include the reason..
Oh well.. the command still functions so I'm personally not too concerned. =)