Thanks, that was helpful. FYI, the solution suggested in the linked thread worked, except that when I put certain outfits on, the problem recurred. It's almost like the problem is linked to certain outfits, and then "infects" other outfits over time, odd as that sounds.
Unsurprisingly perhaps, switching to the Phoenix viewer also cures the problem, but it recurs when going back to the Linden viewer.
My graphiscs card is a Radeon HD 6410D.