Wirelessly posted (iPhone 4: Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_1 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8B117 Safari/6531.22.7)
I have seen that from time to time. I believe you have some calendar entries not tied to anything. I turn off my calendar on the iPhone and say delete all entries and turn it back on. That usually does it for me.