Okay... I got it back... I downloaded the WZR-1750DHP firmware from the DD-WRT site (first installation file) and using the Buffalo WZR-1750DHP firmware web UI, it actually took the firmware file and upgraded it to the vanilla DD-WRT firmware (relief)... from there, I then flashed the Buffalo WZR-1750DHPD firwmare, did a factory reset after it finished, then restored my config file I backed up before I started all this mess this morning (:
So I'm now back on the official Buffalo DD-WRT firmware.