...
>Dec  3 21:10:17 twcsds001       Parity Error
>Dec  3 21:10:17 twcsds001 scsi: [ID 107833 kern.warning] WARNING:
>            /sbus@b,0/QLGC,isp@0,10000 (isp2):
>
>We have replaced all the Ultra SCSI III (sbus) cards. These are the latest
>cards Sun has out. We have upgraded IBMtape, the library code and the tape
>drive microcode. The IBM CE's can exercise the drives without any problems but
>we can't open the drives with tapeutil. We are at loss what to try next. Any
>suggestions are greatly appreciated.

Linda - Your added info, particularly about tapeutil not working, jogged some
        memories of postings from about four years ago.  Rummaging around in my
QuickFacts, I dredged up:

"... Or it could be that the same device is defined as being accessed by
 multiple device drivers: you run happily for weeks, and then some other
 facility goes to access the device, which causes the other device driver to be
 loaded which supplants yours."

I'm wondering now if that's what's happening.  I'm not a Solaris guy: perhaps
there's one out there who could lend more.  Possibly, incidental OS maintenance
work by your Solaris people is inciting the problem, or happenstance use of a
seemingly unrelated tape drive in that same system.

One thing I came upon in researching this which may or may not help:
In the  IBM Ultrium Device Drivers: Installation and User's Guide  manual,
in the  Solaris Device Driver (IBMtape)  chapter, Special Files section,
there is a description of a "...device hierarchy established to support I/O for
an IBM SCSI tape subsystem".  This may help validate what actually has control
at the moment.

Wish I could help more definitively,   Richard Sims, BU