I use Mac OS X Snow Leopard (10.6.8), and here's my problem: Stack and grid views of folders very often look like this:

These empty boxes are not very useful for finding files quickly. When I open a such a view, I notice high processor usage by processes
QTKitServer
diskimages-helper
I assume that they are busy with loading/generating icons and previews for my files. These processes often use the CPU for minutes, but very few icons are generated. Icon and preview generation never seems to get finished for a folder. Does anyone else experience this? Is there a way to fix or speed up this process?