pages are blank now

Hi there,
I have this problem since yesterday or 2 days ago (not sure). My internal pages are mostly blank. The header is displayed, but the content not! Example: http://sardiniatravel.net/holiday/santelmo-residence/
Only the title is displayed, then all blank and the menu is not working. These are custom post pages.

I am using mqtranslate for several weeks now and all worked fine (before I used qtranslate). Maybe since the last update?? I remember there was an update 1 or 2 days ago.
I had deactivated ALL plugins. Then the page was completely blank. I activated only mqtranslate and the same half-blank page as before. So, I guess it might be mqtranslate. when using an html validator and putting in the URL, I always get an “internal server error”. Geeez… all worked fine until some days ago.

Any idea/help?

thanks, marc

https://wordpress.org/plugins/mqtranslate/