my thomson is locking up ?

I have missplaced the booklet on it and I have used all the minutes on record but when I try to delete recorded stuff ,somtimes when I press the blue button(delete) the correct dialogue comes up and then when I press the green to delete completely, the dialog disappears and it locks up.
Sometimes I just go int library and scrole down to the 1 I want to delete and it locks up.
In both cases I have to turn off the unit to be able to clear the memory ,otherwise it stays locked up.PLEASE CAN YOU HELP ME
this is the best bit of kit I have ever bought being able to record while watching something else and pausing live programs ,if visitors arrive.