Why is my computer suddenly doing this? It started a few days ago.?

I have installments that have been in my computer for quite some time like (paint.net, gimp, microsoft office word, etc). I was always able to bring them up easily when I wanted to use them. But one day when I opened paint.net it said "sorry but an error has occurred. Send error report?" Or something like that. I thought it was just paint.net but then I found out all my others were doing the same thing. None of them open up and instead it says error and that send or don't send, thing. Why are they all suddenly failing at the same time?