>we have exactly the same problem, about 2 -3 tapes / day with write
>error, 2/3 of capacity. Only on Imation tapes, not on IBM ones...

Interesting.  LTO divides its tracks into four bands, which it writes
from inner to outer (analogous to optical media).
See http://www.ultrium.com/newsite/html/about_tech.html for pictorials.
Inner bands are inherently more reliable because they are further from the
edges, where more things can happen.  If you had the opportunity and time
to dissect the problem Imation cartridges, you *might* find rippling or the
like near one edge.  It may also be the case that Imation did not properly
create some of the outer servo tracks.  We've had problems with Imation
3590 tapes as well, so you may want to stick with The Ultimate Vendor.
Don't hesitate to return data-obliterated cartridges to Imation, to incite
quality control reviews.

  Richard Sims, BU