Pink overlay on some prims

Hi,
I hope this is the right place to ask this:

Last night when I went to several of the shopping areas, most of the additional prims (i.e. panels showing the textures in a shopping mall) had a pink overlay. The rest of the graphics - street, buildings, avatars ect. were fine.
On an almost identical computer everything looks OK.

On my computer I've swapped monitor and graphics card, removed Second Life and re-installed, and still get this problem.
Everything else on the computer - graphics ect are fine its just Second life
Any suggestions....
Please

Have you tried the following keyboard combination: CTRL-ALT-T ?

It's for toggeling/viewing transparant textures.

Thanks for that tip - may be useful in the future.
Actually finally did a side by side comparison with my two computers (and an alt avatar) and found "Beacons always on" set on my computer. Switched it off and everything is fine.

I really hate programs where there is no manual