iCal refuses to open

When I try to open iCal, it now gives me this message:

"iCal cannot be opened because of a problem. Check with the developer to make sure iCal works with this version of Mac OS X. You may need to reinstall the application. Be sure to install any available updates for the application and Mac OS X."

I suspected at first that this was because I deleted some applications the other week, such as address book and mail, but when I reinstalled iCal from the OS X dvd, it still didn't work. I can't seem to find any relevant updates on the website, which has proven surprisingly confusing.

I am running OS 10.6.5 on a 2.4 Ghz Core 2 Duo unibody MacBook.

Please help. I would like to get organized.

Thank you

Maybe you should reinstall 10.6.5 from the Combo Updater on Apple's download site.

Thank you, it really was that simple. I guess I was just downloading the wrong updates before. I'm a bit confused by automatic updates didn't cover that.

Alright! Always try the simple stuff first.