If you use the MK3 and are not able to load any hombrew apps that use the WiFi functions of the DS (such as DS2key or Win2DS or Wifi_Test_Lib), then here is what you do:
1. use Neo Power Kit to erase everything on your flashcart, and then burn the first ever NeoFlash MK2_mk3 menu... (this would be v0.1)...
2. Format your SD card with Fat16 (on a windows xp machine it will say just plain old "Fat")
3. Put the homebrew you want to run on your SD card manually
4. Plug everything up to your DS
5. Turn your DS on (of course)
it should let you run WiFi homebrew...
all of the other versions of the MK2_MK3 menu do NOT work with wifi... and a Fat32 formatted SD card will not work with v0.1!!!
*jake*
(PLEASE NOTE... this worked for me, and i am using the NeoMax 1gb package... i am not using M3 or G6...)