Now that you found the buffer, where was this 150 thing? I'd like to know that.
When you use the monitor button in Cubase its good to know which plugins are active. Some plugins like SIR 1 have a latency of 8960 samples. So no matter what buffer you set the system is delayed 8960 samples.
Go into plugin information and see which latency your used plugins cause.
Disable the one with the highest latency and see if it gets better then!
Scroll around and look which active plugin has the highest latency and tell us.