Thanks you for your input!
So I already changed a lot the driver mode to all possibilities (ASIO, MME, WASAPI shared, WASAPI exclusive and WDM/KS) but those didn't seem to work. Today I just restarted Cakewalk again, changed it to WASAPI shared and suddenly it works again!
I'm glad it's working right now, but I don't understand why the sound is fine right now, but a few hours ago, with the same driver mode, it didn't work. Is it something depending on my machine or Cakewalk? (maybe a noobie question, but I'm just trying to learn from this situation )
Cheers!