If your getting the black screen of death loading latest games MadWorld etc.try this.
Enable the upgrade option in the config. menu of the WasabiDX (switch off, switch on, press reset 3 times. Disc channel will show GC boot, press start to enter config. menu)
Now by inserting game that black screens you'll get the message that an update is neccessary, update.......sorted, no more black screen, new games will boot.
Dont forget to disable updates again in config. menu

Worked for me
The ONLY reason you SHOULD NOT update the firmware is if your running homebrew and want to continue running homebrew.