I'm unsure why, but when I use the zpMasonry theme, the featured image kind of glitches and covers up the menu. On top of that, if I actually have an image uploaded the whole thing crashes.

None of the other themes I have seem to crash including other themes made by Gjr, so I'm not really sure what's wrong.

I have all the useable plugins enabled, so I don't think it's that.

Not familiar with this theme and how that does it but you might need to do a database refresh (admin overview button) after you uploaded the image. Probably the image is not "discovered" then.