iCal will not open on my MacBook Pro running OS 10.7.4

I have been experiencing the same problem since last Friday. I have tried the following:

• Cleared all Application Support files, cache and calendar files in my user library.
• I have repraired permissions, twice.
• Removed iCloud configuration in system preferences.
• Tried multiple user accounts.

All of these things have not worked. I would love to know if anyone has experienced this and actually fixed the problem.

Same problem with me- tried all of the above to fix it myself and it just won't start. I might try a reinstall of iCal only.

Also have noticed since upgrading to 10.7.4 that my browsers, Safari and Firefox, take much longer to render web pages!!!

How do I go back to 10.7.3???