ICal won’t change what calendar events are saved on

My usual issue goes something like this:

• Click to add new event, under the default calendar
• Add details, etc, and save

Later on, when I want to move it to a different calendar, I edit it, and change it to a different one via the drop-down.

• Make edit, click done
• The event will change to the proper calendar
• The event disappears
• The event reappears under the original (default calendar)

All the calendars are on Google Calendars, and synced via CalDAV into iCal as delegates. I've never had an issue up until a few months ago, and now I have to sign into Google each time I want to move an event.

Running OSX 10.7.5, iCal 5.0.3

Any suggestions?