problems with E.coli heat shock transformations - (Nov/08/2007 )

Here is the thing:

I´ve got competent BL21DE3 cells, have transformed through heat shock, the cells have grown overnight in LB-Agar-Amp (80 microg/mL), but when I take the growing ones and put in LB-Broth-AMP (same concentration), they do not grow anymore!!!

what is going on????

Are the plates and LB medium all freshly made? How big is the colonies? Make sure the amp in the LB plate is still good.