tried PowerSwitch ... it works without any problems.
Then I compared the Makefiles. Only difference I could make out: OBJECTS in PowerSwitch defines usbdrv/usbdrv.o as an additional object (USBaspLoader doesn't. If I add it it gives me a lot of warnings).
main.c-diffs: A few includes. PowerSwitch uses a timer. Besides of that I couldn't make out any major differences. I really don't know what else I could do
Disabling features: Are you talking about the bootloader-settings in bootloaderconfig.h? (HAVE_EEPROM_PAGED_ACCESS, HAVE_EEPROM_BYTE_ACCESS, BOOTLOADER_CAN_EXIT) If so, I deactivated them: no difference.