While waiting for Mozilla Sunbird to at least get to a more advanced beta stage, I'm still relying on my old trusty calendar program, Sidekick 98. And I really rely on my calendar because while I have a head for figures I have no head for dates.
Sidekick 98 has been temperamental lately, especially on my office computer, and I've wondered if that might be because that machine has less memory than my home machine, I run lots of things at once including memory hog wordperfect, and my calendar file must be enormous. If that's right, possible solutions are to start a new file with less data (but that means a lot of manual copying of annual events and all of my life for the next N months) or move to the still-pretty-beta Sunbird (ditto on the copying) before it feels robust and full-featured enough to rely on.