Cal of Duty is likely to have many people on it; and its always going to take a little while to load up the users. High Ping can be caused by many other people having Dial-up; as they take longer to recieve what you're sending out. I can't think it would be your computer if its working ok on most other things.
What is your bandwidth?
A Knight is sworn to Honour. His heart knows only Virtue. His blade defends the helpless. His might upholds the Weak. His word speaks only truth. His wrath undoes the Wicked.