I having troubling understand what other interrupt firing besides TMR2 on PIC18f4550
If I understand right, then when you comment the first (larger) bit out and uncomment the second bit it toggles at 0.7MHz?
The interrupt flag is not cleared so it will immediately jump back to the ISR. The second bit is not in an if statement so it will always be executed. So it will keep setting the pin in the interrupt_at_high_vector and clearing it in high_isr. 
You need to make sure the flag is always cleared (if it is not cleared automatically)
What are you wanting it to do?