Yes, I also got rid of the "data storage full" error when I removed the CalDAV account with the full Google calendar ID.
Unfortunately selecting the 2nd calendar with "iphoneselect" and using the short URL https://www.google.com/calendar/dav/ still gives me only one private Google calendar.
Maybe this has to do with the 2nd calendar not owned by me but rather shared/subscribed from some other person?

http://talk.maemo.org/showthread.php?p=1215122