tactic trainer not responding

i always enjoyed tactic trainer, but since 2 days it seams often not working.

it doesnt notice that i have moved and keeps waiting, while i cannt do anything since i have moved, worse if i press F5 in firefox i get a new problem but the clock keeps thicking as i'm still in the previous problem.

what can be wrong ?

i'm using windows 7 with firefox  portable 3.6.3 and the latest java updates.

this always has worked fine for me

does anyone knows a solution ?
or do other have similair problems with tactic trainer?