Hi guidoterlouw,
usually this error is thrown when the Quilt you are trying to load (the customised one you mentioned) has an issue - or is unable to find some components that are defined in it, or is using components that are not meant to be used in that specific context (for example , if you place some ideas components within a blog).
Have you double checked this? A quick way to check would be to create a custom blog page that replicates exactly the standard blog page (in terms of component) and then set it in Admin. See if that works, if it does then you can change components one by one until you get the error - that will help you in narrowing down the issue.
Thanks,
