I need to re-boot my computer?

I am unable to re-boot my computer fully. It gets to a certain point and then says it can't go any further. It's a while since I tried it, but the only thing I remember that happens all the time is when I switch on, a message allways comes up saying "Delivery manager has encountered a problem & needs to close". As this anything to do with it & if not, what is the delivery manager?