What happened to my tablet's pressure sensibility?

Like, really...My tablet used to have some kind of pressure sensibility thing when I'd use it in GIMP and Photoshop, when I'd use the paintbrush. Now, all of a sudden, the tablet (and even the one from school that I borrowed) make all the lines hard-edged, no matter the pressure, as if I'm using a mouse. What's goin' onnn? It's kind of frustrating. Is there any way I can fix this problem? :(