how to handle multiple interrupt in Gnu compiler

dear,
friend

How to handle Multiple Interrupts in gnu compiler in windows 98?
i have used 5 interrupt which are
timer 0 ,timer 1, UART,USB,SPI.
i have developed code using with these all features including LCD display, EEPROM,Ethernet.
and it is working also.
but when i am trying to add something new means any new structure or variables then only LCD part is work while other part like USB and Ethernet is not working.

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