This is a classic driver fault symptom. At the risk of pointing out the obvious:
1) Have you double check this procedure: http://www.marian.de/files/trace_alpha/win/readme.htm
2) Has a Windows update replaced the driver with a Microsoft generic driver? Check under the legacy control panel, device manager, sound, then click you card and check the driver to see if it is the one you loaded. If driver is generic you will need to reload the Marian driver then use the Group Policy editor to stop Windows replacing the Marian driver in future.