Serial.print messing with Timer Interrupts

[nickgammon]

But if I add Serial.print statements outside of all interrupts and if the statements print more than ~100 chars per second, then I start to miss some of the timer2 ticks.

You say you are printing at 115200 baud. At that rate each character will be clocked out at 87 uS. How much Serial.print are you doing at one time? The Serial.prints are actually sent in an ISR, so they will be affecting interrupts.