I have yet to find a working firmware that actually supports the 1.4 firmware update. Can anyone lend me a hand and help me find a solution to this problem?
It's not the firmware that supports it. You have to update the flashcart using the Acekard's DSi 1.4 update. After that you can use what ever firmware you want again. The update can be found here: http://www.linfoxdomain.com/nintendo/ds/dl.php/AceKard_2i_firmware_v1.4.zip You have to use a DSi without the 1.4 firmware, or a DS Lite to run the update. There are two updates in the file, one for the DSi, one for the DS Lite, run which ever one you are using to do the update. After you do the update, your Acekard will work on DSi with 1.4 again.