One possible cause of this error is a missing design element(such as a view)
from a URL.
For example the url (http://server/db/viewname/document?opendocument) would
work fine. Change the viewname to a view that doesnt exist in the db and you
can cause this error.
Not sure why you don't just get some sort of "design element not found"
message, but I was able to reproduce the error by doing the action above.
One possible cause of this error is a missing design element(such as a view) from a URL. For example the url (http://server/db/viewname/document?opendocument) would work fine. Change the viewname to a view that doesnt exist in the db and you can cause this error.
Not sure why you don't just get some sort of "design element not found" message, but I was able to reproduce the error by doing the action above.