oops I meant tiles
I just went back and tried it again and tiles instead of thumbnails is the correct answer.
In view choose tiles and then file|close
The file|close is what saves your settings. If you just click the X your settings dont always get saved correctly.
Ive been messing around with it today, and have discovered that it works on all themes, and also that it only happens on my account. I went into Safe Mode, and logged into the Admin account, and it was normal on that one.