USB_Init() no longer calls sei() to enable global interrupts - this must now be done in the user application once all init code has run.

Bootloaders/DFU/BootloaderDFU.c

@@ -101,6 +101,9 @@ int main(void)
 {
 	/* Configure hardware required by the bootloader */
 	SetupHardware();
+	
+	/* Enable global interrupts so that the USB stack can function */
+	sei();
 
 	/* Run the USB management task while the bootloader is supposed to be running */
 	while (RunBootloader || WaitForExit)

Bootloaders/DFU/BootloaderDFU.h

@@ -43,6 +43,7 @@
 		#include <avr/pgmspace.h>
 		#include <avr/eeprom.h>
 		#include <avr/power.h>
+		#include <avr/interrupt.h>
 		#include <stdbool.h>
 	
 		#include "Descriptors.h"