Partially working now
Hey all,
Well, I was relieved to see this thread and know I wasn't alone in my frustration. I did get mine working somewhat, so perhaps this will help.
In my case, iTunes had reverted to not synching any of the items on the Info tab. I re-enabled this and did a sync, which got the Mac and iPhone in sync fine, as you'd expect.
I had already reset the sync data through the MobileMe preference pane, overwriting MobileMe data with the information from my Mac. This had no effect on the online calendar though. After I'd synched the iPhone overwriting its contacts and calendar info from the Mac, the information online was updated.
I tested it by adding an event in iCal, it showed up on the iPhone a few seconds later. I've tried it a few times now and it seems to work fine, showing up just as the auto sync gets going.
The online MobileMe calendar doesn't seem to be picking up the changes and changes I make on the site don't show up on my phone, so I'm not sure what's up there.
Anyway, I'm happy enough for now, I hope this helps some of you.
Good luck!