iCal problems

Ok, I have never done this, so here goes. I have had a Mac for several years and I have been relatively satisfied. Now, I am about ready to pitch it. I have been having serious problems with iCal. Either it quits unexpectedly immediately after being opened, or it hangs and won't open at all. I also have hundreds of blank/empty calendars. I don't know how they got there and I can't get rid of them. I deleted them manually at one point - one at a time using the delete button - shortly thereafter, they reappeared.

I have a subscription to .Mac (now Mobileme). It appears I may need to cancel the subscription as the syncing may be part of the problem and there appears to be very little support out there for Mac OS X Tiger (10.4.11) on an iMac G5 (no Intel dual core processor). Is there any point in paying for Mobileme with a computer that's several years old? I am trying to use Mobileme to sync the iMac G5 with a MacBook 2,1 (Intel Core 2 Duo) and an iPhone 3Gs.

Any help would be appreciated. I am not a techie, so need to keep it simple. Thanks.