I can't exactly use any items in dungeons. The quickslots are greyed out. I have no clue if it's a glitch or just me being stupid and accidentally doing something I wasn't supposed to do or how to fix it--so help would be greatly appreciated! Thanks!
You probably locked your HUD by accident, you can turn it back on with Q (if you didn't change the key) or the lock icon on the top right near the map display.
http://wiki.spiralknights.com/User_interface#Top_right