outlook calender can't update to iphone 4

Hi

after i upgrade my itunes to 11.0.1.12, then, my outlook calender events can't update to iphone 4. (the previous events were able to update to iphone4)

my iphone 4 was IOS5. then, i update calender event from iphone 4, those new events can update to my PC's outlook calender

then, i upgrade my iphone4 to IOS6.1, same problem. Mean, only one way update from my phone to outlook calender; but can't update new event from outlook calender to my iphone4.

this all happen after i update my i tunes to 11.0.1.12 since last month

anyone can help?