What is the lightning bolt icon in iCal?
I've gone through this document, but it's for iCal 3.0, Lion has 5.0+.
http://docs.info.apple.com/article.html?path=iCal/3.0/en/symbls.html
Here's what it looks like, I'm not sure if it's a bolt or a tilde:
Hovering over it gives you no information about it, and it disappears shortly after creating the event...
It means iCal is having difficulty sync-ing with iCloud, or google Calendar. Or some other calendar services that you have.
It means it from a calendar online and you're not currently connected.
It's the same icon as in Mail for an unconnected account.