put your r4's kernel into a 8gb micro SDHC 2gb micro SD card and put acekard's updater in - both in the root of your micro SDHC card. boot up into your r4 and locate the updater; load it, just like loading any game. While in the updater's menu, it will allow you to eject your current flashcart and insert your acekard. Do so, and proceed into updating. After the update, your acekard will be un-bricked and also updated.
EDIT: never mind. buy a cheap 2gb micro sd card for your r4 and do the above.