2001 VW Passat Oxygen Sensor Check Engine Light

Hi. I'm having a problem with my 2001 GLS Turbo Passat. A few months
ago, the check engine light and Emissions Workshop message came on.
The first VW dealer we took it to said it needed a oxygen sensor, mass
air flow sensor, and something else I can't remember. Seemed odd to me
that three parts would fail at the same time, so we took it to another
dealer. They said it was a faulty computer, which was covered under
warranty. They replaced it and everything seemed fine, for a little
while. A short time later, the check engine light came on again. Took
it to Autozone to see what code was being returned. Said it was the
oxygen sensor in bank 1. Having lost confidence in the VW dealers,
took it to a local, trusted garage. They too got a bad oxygen sensor
code. They replaced the oxygen sensor and reset the light. After
about 30 mins of driving, the light came back on. Took it back and
they hooked it up again. Still said bad oxygen sensor! Not sure what
to do next. The car won't pass emmisions with the faulty code. Is
this a known problem? Is there some trick to resetting the code
correctly? Any advice would be appreciated. Thanks!