Just solved problem. Close itunes 11. Install iphone 5 with serial cord. Open itunes. Iphone devise will be recognized in upper right. Click on it and menus will change such that info tab appears in upper left. click on it and you have access to menus for sync of calendars and contacts, etc. Worked for me, hope it does for you.
I have the same problem. This is very recent, and seems to be because I upgraded the OS in both cases. Before I did that, everything was fine. So, now, any event that I input on the Iphone 3GS fails to show up on the Macbook Air. Not only that, when I tried the override button in Itunes, as my calendar entries in the computer were now newly made, it would not synch it on my phone.
The final straw is that any calendar invite I get, refuses to be assigned on my calendar...
Took it to the Apple Support folks here, and after 3-4 hours, all they did was what I told them I had already done - to do a full restore... nothing happens. In fact, whenever I do this, I get an additional repitition of calendar entries from the older events... so, I have 6 anniversaries of my own now, and 3 birthday renditions of my friends - on the same date... !