Windows Explorer Crashes in Thumbnail View (sometimes)

I'm using XP Home Edition and am having a problem with 4 folders (out of about 500) that I use to store images downloaded from the net. When I open one of the folders in thumbnail (or filmmstrip) view Windows Explorer crashes (get one of those "Windows has encountered a problem and needs to close.." messages and I don't have the problem with any other type of view mode: list, details, etc., which display only an icon instead of a thumbnail). This will also happen after "Right click, Save as" and browsing to that particular folder (using any browser--I use the latest versions of IE, Netscape and Opera).

Since the problem only started recently, I tried deleting the last few files I downloaded but this had no effect. Several scans of my computer with Norton have not turned up any viruses.

And not all programs that display thumbnails cause this problem. Photoshop's File Brwoser runs just fine and I use a freebie image viewer called iBrowser without a problem. But Ulead's Photo Explorer crashes just the same as Windows Explorer.

Any suggestions? I've searched Microsoft's knowledge base to no avail.