EINVAL on write to an exabyte tape

[Russell J Fulton;ccc032u]

We are running 3.3.1 and I am having trouble with a program that writes ANSI 
labels on tapes. I am fairly certain that I used this program on 3.2 but
it was never used extensively because of the bug that caused exabyte drives
to rewind when used by tar or bru.

Now when I try to write an 80 character label on the tape I get the error:

EINVAL - attempt to write to a stream linked below a multiplexor.

What does this mean?

Russell.
-- 
Russell Fulton, Computer Center, University of Auckland, New Zealand.
<rj_fulton at aukuni.ac.nz>