The blackout bars occur whenever I'm already in truetype and scroll through/select a unit. In that case, it seems to extend a black box (the background of the text) further out to the right than it should, occluding any words behind it (i.e. when I go to the unit list screen to scroll through my dwarves, it blacks out the job behind the dwarf sometimes as I scroll down. It's not for every single line, but it IS always the second dwarf at least).
So, turning off true type yields the obvious horrible giant blocky text in menus, fraught with repeated tiles for certain things (like the grate tile and number sign tile being the same).
I'm assuming you can't disable custom graphics on just the menu portions. As of now, this is basically unplayable for me (my only two choices are either large portions of my text are outright missing, or the menu is just way too blown up to read when not in truetype, leading to words being compressed to ridiculous, unreadable lengths).
I don't suppose there are any other workarounds aside from restarting the game a lot, because I'd much rather use this tileset than the default ASCII.