You may get this error if you have installed Digital Performer 2.5 but you have not updated your PCI-324 driver. On our downloads page at motu.com you can choose 2408 drivers. Download MAS 1.5. From that installer you can custom Install the PCI-324 driver. Restart and then try choosing the PCI-324 driver from DP 2.5. In the extensions folder there is a MOTU folder. In that folder you can get info on each item and make sure you have the latest. After installing the latest PCI-324 driver you should have Motu Audio System 1.5, Motu Public Objects 1.22, and PCI-324 Driver 1.3.