Hey this could be related to a problem I had found out recently. Right now there's a bug with laytheme: You put project thumbnails inside a category page. Then you edit those projects but they are not members of that category (by using the category checkboxes inside the project edit screen), then the project will be removed from the category overview page when you save the project :/.
Will be fixed soon with a new update :D.
If that's not your problem you can write me your website address and login data to armin.unruh@gmail.com and I will check it. Please also provide a link to this topic so I know what to look out for.
