you can semi-brick your ps3 if you update incorrectly or mess up the process. you then won't be able to turn on the ps3 as it will just give you an almost musical beep.
you will also not be able to turn off service mode with the second self file either. nore can you update again as youve most likely turned off the ps3.
the fix is simple though, just hard reset it and try to re-enter service mode. sometimes it won't work and sometimes it will - it took me two tries. when youre in service mode (you can only tell by the dongles light) - try the whole process again but use the modified 3.41 update.