Recently, the domain for Marbleland needed to be changed for a variety of reasons, but this is what is causing the message to appear on everyone's screen. The current version of PQ is still looking for the old domain name for the custom level list, but since this domain does not exist anymore, the game doesn't find anything to load. Marbleland integration will not work until a new version of PQ supports the new domain name and this will hopefully happen in the next 1-2 weeks.
Don't worry, you can still download levels directly from the Marbleland site and play custom levels from there. It is only the in-game downloading option that does not work at the moment.