> set blocksize to variable (blocksize=0).

Doesn't seem to help.  Though it did change the error:

Jun 23 09:23:38 zen /netbsd: st0(aha2:5:0):  Check Condition on opcode 0x8
Jun 23 09:23:38 zen /netbsd:     SENSE KEY:  No Additional Sense
Jun 23 09:23:38 zen /netbsd:                 Incorrect Length Indicator Set
Jun 23 09:23:38 zen /netbsd:    INFO FIELD:  -5120
Jun 23 09:23:39 zen /netbsd:      ASC/ASCQ:  No Additional Sense Information
Jun 23 09:23:39 zen /netbsd: 
Jun 23 09:23:39 zen /netbsd: st0: 10240-byte record too big

Its hard to tell what state the drive is in, I just did:

: sjg:214; mt -f /dev/rst0 blocksize 16384             
: sjg:215; mt -f /dev/rst0 status          
SCSI tape drive, residual=0
ds=0
er=0
blocksize: 0 (0, 0, 0, 0)
density: 19 (0, 0, 0, 0)

which is the same as it always displays.

Very odd.

--sjg