Under Photoshop's Preferences > File Handling > File Compatibility, do you have
"Maximize PSD and PSB compatibility set to "Always" ?
If not, set it to Always and re-save your file. Turning a layer on and off counts as a savable change.
I want to thank you soooo much for this solution to this! It totally worked!
Thanks for letting me know. Sometimes it's hard to tell if the answer works for a certain setup.
I just realized that I have that problem with illustrator CC files too. Do you know what may help those?
I had success with Ai's File > Save As... command on .ai files that have no preview and show only the .ai logo.
File > Save on non-preview files keeps the old properties, while Save As...creates a file with the new properties including the thumbnail preview.
In the Save As... dialog, I use Version: Illustrator CC (17.0) and check Create PDF compatible file and Use compression.
I'm running Mavericks 10.9.1