modelsim vsim-3601 on counter

This behaviour happens with the tesbench (which just sets the clock and hits the reset at the beginning) and simply through forcing the clock/reset directly.

However, perhaps this piece of the puzzle will mean something...when I single step, I do not get this error, and the counter increments, pulses the fullcount, and resets itself fine. Doesn't get stuck in any loop. But running it for any time results in the iteration error. At some (seemingly random) point, the wave stops drawing, but I still see the signals incrementing as they should.

Thanks for your thoughts/help,

Michael