Having bypassed Apple techs who suffer from learned helplessness and transcended mysterious generalizations, I have fixed the problem. But it took a little patience and creativity. The fix involves a single overhead transparency sheet, some scissors, a little scotch tape, and Brian Eno music.
I took an acetate sheet...the plastic sheet one writes on in using an overhead projector, cut "T" shaped pieces, and layered them together. Depending on the ribbon connector...there were two I specifically had to shore up: the trackpad connector and the USB board connector, I used 5 and 3 layers, respectively, get the ribbon cables in...and snugly. A little tape here and there between layers should prevent movement for a while. Remember: The retainer clip is a little wedge-type thing with hooks on either side that keep the ribbon cable seated against the logic board connector. The layers of razor-thin acetate, put together and anchored with a little tape, add up to something just slightly thicker than the original retainer clip.
What amazes me is that these tiny little things are made of fairly brittle plastic and so HARD to find. Not even Apple seems to know where they are. They're probably made in China with a lot of lead in them to boot.
This worked like a charm, thanks to 3M; no thanks to Apple-trained techs who told me to "Google" it.
