Ical frozen - blank screen, no data and unresponsive buttons

After installing the last update, Ical is frozen - its shows no calender data, and the buttons for day/week/month don't work. I restored the calender data from my last time machine backup, after which it worked for the first time I opened ical. The next time I opened it, I was back to square one - no data, and unresponsive buttons (also not able to change the view over the top bar menu) and then I even got a blank screen (where the calender data should be).

Luckily my data still shows on my iphone and on my google calender. Its only on my Mac (version IOS 10.6.8) that Ical (version 4.0.4 (1395.7)) isn't working. I believe this is a bug of the actual Ical software, rather than my data.

Anyone have similar experiences, or an idea of how to fix this? Thanks.