Hold down one of the buttons next to the Jog-roller (I can't remember if you have to hold down the left one or the right one! ) and poke the reset button.
You'll know it's worked because the Graffiti Area will be this scary grey rectangle - Don't worry 'tho, it still works (If you tap where the Home icons should be for instance, it will goto the launcher screen)
If you're using the Clie Organiser as your main start application 'tho, you might need to either make the main launcher the default first, or bind it (or something else like FileZ or Clie Files) to one of the hard buttons
My 18month little girl somehow did something when she grabbed at my wife's TH-55 and now it continues to pop up a empty reset dialog box and if I try a warm reset it does the same thing with the one button and the other button with a reset locks the TH-55 off (power button does nothing). Is there something I'm missing?