Zero Response from Steinberg since Feb 22nd

I have been having severe problems with stuttering with Cubase Pro 8.5 when I decided to pay for the upgrade to Pro 9 in the hope that this might solve the problem.
Regrettably, the new version 9 is stuttering just as badly as before - perhaps even worse if anything. This happens during playback and recording.
This is a very disappointing, annoying and serious problem that I really need to solve as soon as possible. It’s bad enough for me to have started looking at other packages despite having been with Cubase since the early nineties.
I raised a ticket with My Support on February 22nd and again on March 23rd but haven’t even had the courtesy of any acknowledgement at all from Steinberg - almost 7 WEEKS have now passed with zero feedback.
I have tried various suggested solutions on the Forum regarding ASIO etc to no avail.
Can anyone help further?
Also, how long should I reasonably expect for a response from Steinberg?