Adaptec 2940 controller/alad driver

We recently installed SCO Open Server Network 3.0 on an EISA bus dual-Pentium system with 2 Adaptec AHA-2940 SCSI controllers using the alad driver supplied by Adaptec. Since our initial configuration (end of April) we have received unrecoverable SCSI read/write errors from time to time. I have replaced two hard drives and one controller card at different times (we only have 4 disks, two tapes, and a CD-ROM on the system). Right now my thoughts are that either there is a problem with the alad driver or with my PCI slot. Has anyone else had this problem? John Prideaux alastl@ix.netcom.com