iCal crashes since I started using iCloud

Hello,

At the moment I have an iPhone 5 and a MacBook Pro with OSX 10.7.5.
Today I wanted to install an app on my iPhone which can trace the location of your Apple devices. For this, an iCloud-account was required.
So I created one, and while I was working on it, I thought I might as well use iCloud to sync my e-mail, contacts, and… iCal. Here's where the trouble started.
On my MacBook Pro I now can no longer use iCal, because when I open it, it starts syncing my Calendars and appointments and then crashes. However, I can still open iCal and my Calendars and make/change appointments when I use my iPhone or when I go to https://www.icloud.com/#calendar.
So I assume the problem is caused by the syncing? Unfortunately, I can't switch off this function as iCal won't open and I can't edit it's Preferences. Also, when I go to System Preferences > iCloud, there's the overview of whatever is syncing. But the switch for Calendars does not respond, the only thing I see is that this Calendar syncing is "starting".
On my iPhone, I can go to Settings > iCloud and switch the syncing for Calendar off. But this doesn't solve the problem with iCal on my MacBook Pro.

So, is there any way I can force this syncing to quit? Or is there any other way I can still access iCal on my MacBook? Any help would be welcome!

Problem is solved now, thanks to Apple Customer Service.