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/CDC/BootloaderCDC.c

@@ -69,6 +69,9 @@ int main(void)
 	/* Setup hardware required for the bootloader */
 	SetupHardware();
 
+	/* Enable global interrupts so that the USB stack can function */
+	sei();
+
 	while (RunBootloader)
 	{
 		CDC_Task();