I am having the same issue. I'm running Snow Leopard 10.6.5. on a MacBook Pro. From time to time the icons on my desktop reduce in size to 16 from my standard 32. As well, occasionally while i'm browsing the internet, my browser content shrinks for no apparent reason.
I'm wondering if anyone has a reason/remedy for this glitch.
Why does Finder keep shrinking the size of the icons on my desktop? I set them for 48 X 48 and a few minutes later they reset spontaneously to 16 x 16. Irritating