Dimmer switch repair?

Hi, I have a dimmer switch which has a touch/remote control senser (rather than a button). I didn't fit it so I can't provide any better details on make or model I'm afraid. It was working fine but now when I put my hand to it the light flashes on then off again. If anyone out there can explain why this is happening and what I could do to fix it I'd be very grateful. Also, the senser has always been slightly warm to the touch. I've assumed this is normal, am I right?!

Jude
April 2007