Just got the same error message on my Hotpoint WT741, and found that switching it off and on again at the wall (not just at the control panel) allowed it to be restarted. Whether it will perform past the part of the cycle where it failed last time is as yet unknown, but so far, so good.
No idea what F - 12 means, but find that off-and-on-again seems to soothe the most tiresome electronic beasts.
Lime, January 2008