Cubase Vst 5/32 Vs Delta Audiophile 2496 Options

I´m using Cubase VST 5/32 with a Delta Audiophile 2496 Soundcard and there´s a problem:

The card will play the sounds just fine for a few minutes, but after a few minutes, it starts distorting the sound, it gets all cracked up, and it keeps growing so in the end it´s totally useless.

I have tried running the sound through the Sound Manager and that has been fine.

Since the "support team" at Delta didn´t respond to me when I asked them for tips and hints, I´m hoping someone here might be familiar with this. I also tried replacing the ASIO drivers, but the same thing happened.
I also tried using the Audiophile as the output in the Sound Control panel instead of the default built-in soundcard.

Nothing seems to help.

Can Quicktime be part of the problem?

can someone help or offer advice?