This problem can be remedied by using DigiSystem INIT 5.1.3cs5 Update (for Mac MIX systems only).Download is available from the Support/Downloads DAE & DSI Download Section: www.digidesign.com following chassis, shipped after January 2002, did not recognize Pro Tools|24 MIX cards when installed. This problem has been fixed. In addition, Pro Tools|24 MIX and Pro Tools|HD users will need to download an updated version of DigiTest (available soon) if they wish to test their setups with these chassis.* Digidesign 7-slot chassis* SBS 7-slot chassis* SBS 13-slot chassisDigiSystem INIT 5.1.3cs5 is still compatible with earlier chassis.Who Should Use This Update?This update should be used only by:* Any Pro Tools 5.1.1 or 5.1.3 user with a Digidesign 7-slot, SBS 7-slot or SBS 13-slot chassis shipped after January 2002* DigiSystem INIT 5.1.3cs5 can only be used to replace the Pro Tools 5.1.1 or 5.1.3 DigiSystem INIT* DigiSystem INIT 5.1.3cs5 may be used in conjunction with any version of the Pro Tools 5.1.1 or 5.1.3 application, but should only be used if your MIX cards are not being recognized by the chassis listed above.