lorien, it bugs me too...
actually... this is something i learned from Uncle Pug on here, and something i plan
to use in the future:
as long as you know how long you've been below 3 ATA's (66 feet) all you have to do
is spend the same amount of time above 2 ATA's (33 feet) and you'll be golden.
a bunch of people have checked this out with deco software, and it holds up.
this does not work with air. you need 32% or higher mix.
this, of course, requires that you jot down or remember the time at which you
passed 66 feet (i'd jot it down; my memory is terrible). also, it requires good
gas management, since you will need gas at the end of the dive to do your
time above 33 feet.
also, the more time you spend shallow ANYWAY is good for offgassing, so i wouldn't
abort the dive. i'd just go above 33 feet if possible and continue the dive.
also, i jot down my NDL for the planned depth (and 10 feet below and 10 feet above,
just in case), and so if my computer fails, i have my watch and can continue the
dive up to the NDL and then begin an ascent, and try to get as much diving as i
can (gas permitting) above 30 feet.
i have to say i have yet to have a computer fail on me, btw.