Occasionally, in list view and column view in my finder windows, filenames are listed but their icons are absent. Absent also in corresponding Get Info panels. Oddly they are fine in icon and cover flow views and folders are not affected. I simply cannot pin this behaviour down to any particular action on my part and, eventually, the icons reappear.

Not a showstopper, but irritating. Any ideas?

andy
21.5in iMac 3.06GHz Intel Core 2 Duo
mem 8GB, OS 10.6.4