Ha, well, I pulled a switcheroo this weekend and fixed my g.f.'s rolling
glass door instead of installing security lights. Need to do a bit more
research and thinking about the lights.

But thanks to everyone for the sliding glass door thread recently, which
prompted me to tackle this one instead. I knew naught about adjustment
screws before, and although I realized there were rollers, I never
thought about the stupidity of lubricating the track.

Her house was built in 1960 and the door is almost certainly original.
Spent a while with rags cleaning the accumulated grease and dirt from
the track, then tried the adjustment screws which made no discernible
difference. Pulled the fixed panel, pulled the roller/slider, expecting
to find flat or broken rollers.

Took me a while to figure out how to remove the mechanisms and figure
out how they were supposed to work. Turns out they were in perfect
shape, but for some reason the axles were collapsed into vertical
grooves, beyond the adjustment ramp. So the adjustment screws couldn't
pull the wheels up the ramp. Cleaned the mechanisms with a toothbrush
and some WD-40, of course, but wanting to be safe I used the old
flammable stuff rather than the new extremely flammable stuff.

Bottom line: spectacularly successful zero dollar repair. Moral: Take
the advice of others here; don't lube the track, fix the damn rollers.
The doors are misnamed.