Nuendo 4 no more sound after bus adding.


I’ve got a really annoying problem with my nuendo. I’ve search online but never find a solution.
When i launch the program and create a new song, everything works, i can add vst and instruments and i’ve got sound, but if i add a new input bus (for my guitar or mics), it immediatly stop the sound in nuendo, no more sound coming anywhere. For a long time, i had ancient tracks with buses created and i was using this as the base to counter the problem, deleting all the content but keeping the created buses and starting from here. But it’s really annoying if i want to start from scratch. I launch addictive drums, click on the kick to see if i’ve got sound, it works, go into vst connection and create a input bus for my guitar and BANG, no more sound in addictive drums or in the bus or anywhere (windows sound still works). I had no messages anywhere but i thing adding buses may cause my audio driver to crash inside of nuendo.
If someone as a solution for this i’m very interested. Sorry for my english i’m french so you may find some mistakes here and there.