I wonder if excess base and/or job XP causes the error... My Ranger and RG have both 99,999,999 base EXP.
your stored exp shouldn't matter. all that means is that you're basically immediately level 151 as soon as you kill anything.
random notes:
dying at pretrans or trans 99 does not lower your stored exp (so be careful if you're trying to stay in Low TI if you change to third class).
however, dying at 150 pre-175 update results in lost exp, and dying at 175 will also lower stored exp.
base exp can be stored up to 99,999,999, I think job exp is a much larger number.