This explains it quite well I think:

amanda@zappa:/tmp$ amtapetype -c -e 35g -f /dev/nst1
amtapetype: /dev/nst1: reading label: Input/output error
amanda@zappa:/tmp$ amlabel ait ait02
rewinding, reading label, reading label: Input/output error
rewinding, writing label ait02, checking label, done.
amanda@zappa:/tmp$ amrmtape ait ait02
amrmtape: remove label ait02.
amrmtape: preserving original database in curinfo.orig.26294 (exported).
amanda@zappa:/tmp$ amtapetype -c -e 35g -f /dev/nst1
amtapetype: The tape is an amanda tape, use -o to overwrite the tape
amanda@zappa:/tmp$ amtapetype -c -e 35g -f /dev/nst1 -o
Writing 128 Mbyte   compresseable data:  42 sec
Writing 128 Mbyte uncompresseable data:  42 sec
Estimated time to write 2 * 35840 Mbyte: 23520 sec = 6 h 32 min
amanda@zappa:/tmp$

I think that this was a new tape, never written to earlier.

Just wanted to file a report so it might be fixed.

/Andreas Sundström