When you tell us a bit more, maybe someone will be able to answer you with
some relevant information. Please read this link and think about what we
need to know to be able to help you:
I have the same problem. Until very recently, clicking the Calendar button
in Outlook would open my calendar immediately. Now, clicking it results in a
lag of as much as 15 seconds before the calendar appears. I share my
calendar by publishing it online. I am running Windows Vista and Office
2007. I hope that is sufficient information.