if you use the old 4.0 system menu file of 00000072.app (NTSC) then it will semi brick and you wont be able to access the settings menu. The system menu for 4.1 is 0000007b.app. I have tested it on 4 4.0 themes so far with no problems.
If anyone wants the 4.1 system menu (0000007b.app) i have...