iCal screen won't respond

The To-Do's have disappeared from my iCal, and when I launch the program, I can make only one change, and then nothing responds. I can't even open the preferences. iCal remains visble, but useless on my desktop.

The only new thing I have done is to sync my Palm m500 and my iCal using iSync yesterday. I tried resetting the sync history in iSync preferences as was recommended on a thread with a similar problem, but with no success.

I have used iCal at work and at home for quite a while and love it. I feel lost without it!