Update I came to the conclusion that the Google Maps widget is causing trouble, because when I remove the widget it loads the page and as soon as I place it back on the page, then the page wont come up, have a solution for that?
@Thijs, I already checked that and it is set correctly
Also I am very sorry for saying it was mendix fault
Thanks for everyone in this thread for finding this issue! Like I said in Mike's thread, it seems this was caused by the new Big Decimals introduced. The Google Maps API doesn't accept those Big objects are actual numbers.
I made a quick patch for this which is now on the App Store! Google Maps Widget v5.3