Same problem here.
I can create a new event in iCal and it will push to google, to icloud -> to my iphone 4S, but I cannot delete an event without receiving the same error. I can successfully delete an event from either the iphone 4S or Google and it pushes that deletion to everything. But iCal cannot do this without throwing up the error. As soon as that error goes up, the "delete" command is lost in cyberspace and the event still resides on Google and iPhone.
The URL brought up in the error code is something iCal used to have a field for before Lion. That field is gone in Lion, and there's nowhere to correct/paste that URL.
I need this to work.
I also have another problem. I'm set up to push multiple iCal calendars to google, iCloud -> iPhone. It's great! Problem is when a new event is created in iCal, iCal creates it in the default calendar (set in iCal prefs) and calls it "new event". I then edit the "new event", giving it a name and assigning it to the appropriate calendar.
The problem is if iCal is online, it pushes TWO events to google. It pushes the initial, unnamed "new event" event, and then it pushes the edited "new event", reflecting the name change and calendar assignment. This is not repeatable on iPhone or Google and appears to be a bug in iCal.
Before Lion, I didn't have these problems. iCal has fewer features and less accessibility in Lion vs Snow Leopard, and I'm surprised it's this buggy months after release.