Problem using st.exe to push data off to tape

I'm trying to use John Wilson's ST.EXE program for DOS to push data off to magtape on my Qualstar 1260S connected to an Adaptec 2902, but it stops with a media error on every tape I try. Here's what I have done: - Created a DOS boot disk with only the aspi8dos.sys driver loading - Defined my TAPE variable as SCSI5: The tape files and st.exe are stored on a fat16-formatted IDE drive. That is all that is on there, and the disk was freshly formatted. Here's what happens when various commands are issued: - st iput filename.ext 512 - tape goes back and forth then stops with a media error - st write - tape goes back and forth and then goes back to a dos prompt. I try to do 'st rew' after this, but then it does what looks like the 'write' operation - st weof - "on line" light blinks continuously. This doesn't always happen, sometimes it does the 'st write' behavior. So, thus far, I have no boot tapes. Can anyone help me out with this? Thanks Julian