Thumbnail Preview Automatic Resize

I'm not quite sure how to name this thread, so hopefully my description makes more sense.

I've been using 7 since its official release, and I'm on my third separate installation after reformat. All reformats were as a result of normal toying around. Basically, in each and every installation of 7 x64 I've installed, video/image thumbnail previews consistently behave unreliably.

Specifically, under normal operation thumbnails are generated, and then Windows automatically removes the dead space around the previews. For instance, when a series of 16x9 previews are generated, Windows would remove the empty space around each thumbnail.

My problem is that Windows consistently and randomly stops removing the empty space around the previews. One second all my previews will be nicely grouped together with no large spaces of empty white between them. The next second, literally, Windows stops behaving well.

I've searched high and low for anyone else that has seen this problem, but I've either not used the right search terms, or nobody has seen it but me. (Probably the former.)

I wondered if anyone else has seen this quirk, and if so, has a cause been identified?

Hopefully showing screens of PBS programs won't land me in DMCA hell. Let me know if this is a No No.

When Windows does what it should, if the previews aren't "resized" to eliminate empty space, refreshing causes Windows to resize everything properly. For me, when explorer isn't behaving well, hitting F5 does nothing.

Oddly, if I use cntrl+scrl_wheel to resize the thumbs, Windows removes the free space. It doesn't last long, though, because if I hit F5 or exit the folder and return again, the dead space comes back.

To be clear, it is common for me to experience this in one instance, and the very next second everything will work properly. Usually I'll have closed an open window and opened another explorer window, but sometimes it rectifies itself within the same open window.

It has really confused the heck out of me for months, but it isn't a massive deal.

I figured they'd be fine, and PBS is free anyway.

As for scrolling, yeah, when Windows is doing what it should that does the trick (as does any # of other things).

A lot of the time it doesn't work for me, and no amount of scrolling, refreshing, etc. will get Windows to snap out of its rut. It'll just keep giving me the same largest size thumbnail space indefinitely. Sometimes for hours, sometimes for minutes.

Anyhow....I think I must do something to all my installations of 7 to get this behavior, although I have no idea what that may be. :)