If you're using the scoreboard aka "tab menu" to preform these actions then as a superadmin you need to look for sever settings at the topright of the "tab menu" and find the "Edit Groups" button (in the middle column IIRC). In here is Fadmin's permissions editor, since I take it you have a custom group or what not... this might be your issue. Give yourself, god, freeze, etc.
However if you're for sure using ulx commands i.e. !freeze, etc. then listen to the above reply and let him know which commands you're using for the ulx extended addon.