anyone else having this small bug/glitch? iOS 4

so i've been recently putting all my apps in folders and sometimes when i slide between pages in the homescreens (don't know what they're really called), the icons for some apps seem to disappear. i can still see the words, tap them, and move them around, however. Either it takes a few seconds for the icon to appear, or i slide out of that page and then slide back to see them.

anyone else getting this? or is it merely just the ipod touch trying to load the image?