another idea, you are using a different part (2455 as apposed to 4550), when you change target device in mplab it resets all your configuration bits, you might wan't to check that you have got them set right in both the 2455 and 4550 versions of your project. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist