Cubase VST cannot properly load the audio card drivers or cannot communicate with the sound card. The Sound card may not have dedicated ASIO drivers or is a poor sound card (ESS Sound Card, Rockwell/Riptide, Meastro Sound, etc.)

1. Check the computer for IRQ conflicts.
2. Reduce the number of running background applications.
3. If the sound card has dedicated ASIO drivers, go to the Audio System setup to switch to the sound card’s dedicated ASIO driver
4. If the sound card doesn’t have dedicated ASIO drivers, go into "Setup MME" and disable the sound card’s synths. Leave only the Midi in and Midi out ports active. This helps with generic sound cards.
5. If using Cubase VST PC 5.0, try switching to the ASIO Direct X Full Duplex Driver (great for Sound Blaster Live cards!)
6. If the error still occurs, suggest using a sound card that uses dedicated ASIO Drivers