Have installed (copied) a few games into wiiflow (wbfs folder) which work fine, sports island as an example, however I am having trouble with some other games such as mario kart and 101 megamix, these work fine from the disk and will install ok, they just won't play, I get an error message such as USB failed -4

Can anyone let me know why this is?, is there a file size limit on what you can install? I would prefer to have them on the sd card as opposed to loading disks all the time

Any help would be appreciated