PIC18 Demo3 problem

When I build a PIC Demo3 on a 18F452 on a Microchip PicDem 2 Plus it work fine (all I did was add 4 LED to port D), the serial out send char "A to X" with out any problems… but when I re compile for an 18F4620 (a larger code and ram base) the serial port sends "A to O", short a few charterers?? I do not understand what can cause this??? Anyone have any ideas??  both are running with a 10mhz xtal and 4xPLL…  baudrate is 57.6kb Demo 1 and 2 work just fine… thanks… tom lafleur also looking for a HD44780 LCD driver and PWM drivers that work under FreeRTOS