Please read this (in particular the section titled "Supply pertinent information for quicker answers"):
What have you done for trouble-shooting so far?
Restoring Preferences after making sure all customized presets like Actions, Patterns, Brushes etc. have been saved might be a good starting point:
Has liquify ever worked well on your computer? If so when? What is your system setup? What OS? How Much Ram? What kind of graphics card? How much scratch disk space do you have? Liquify is processor intensive. It’s possible that your computer can’t handle it well.