A few weeks ago we were facing the situation that in a new deployed Enterprise Portal site most of the existing Enterprise Portal Web Parts where showing the following error message instead of their supposed content:
Also the Titel Web Part was affected by this issue. At the end it turned out that some modification done in the past in the Global::webSessionClient methods were the root cause of this issue. After removing all customizations in this method and performing an IISRESET the Web Parts started to work.
If you run ever into this or a similar issue check if you have any modifications in one of the following methods: