- An extension conflict could cause this. Try changing your extension set to Mac OS Base + Soft SampleCell Extension(s).- The problem extension in one case was the Matrox "loader" (for the RT Matrox)- This can be caused by a conflict between the Soft Samplecell Extension and SCSI hard disk drivers, If an ATTO card is being used, use the Inhibit Driver Loading option in ExpressPro-Toolsand place the ExpressPro-Tools extension in the extensions folder. This will force the hard drives to use the ATTO extension as their driver and will not load their own drivers at boot up. This should allow the Soft Samplecell extension to load properly and allow the application to boot.