Nuendo 6.5?

I just bough nuendo 6 (update from 5) and yesterday was horrible. Just on one mixing the program stoped so many times, that i stoped counting. Changed the Buffer time, nuendo stoped… I open a new plugin, nuendo stoped…Try to save work, “can not save this file because its corrupt”. How is this possible? in one afternoon i’ve encounter so many problems, just mixing one track…How can you release this?? Horrible…
I’m a user sense nuendo 1.0 and If someone wants to buy my nuendo, i seal it for half price. I’m tired of shames in front of customers.