I was able to check this out with the Set Session Value server behavior in the Cookies extension. I can confirm that the splash screen for eCart appears when I do this, but it seems to add it to the page without issue.
It seems that you might be experiencing an issue with a corruption of your configuration folder. If this is the case you will need to follow the steps listed here to undo any corruption that might have occurred:
If you continue to have the problem after going through these steps please post back and let us know.