well i dont know your computer but here are some guesses:
1) you havent fixed your privledges. (there is a bug in 10.2 such that after installation you must boot from the cd go to the disk utility and choose the repair privledges option)
2) you have 'tinkered' with your system by installing betaware, removing extensions, moving items in the library folder (including fonts), or some other 'tinker'
3) your system is in need of fsck -y (boot into single user mode by holding down command-s and after the command line is finished booting type fsck -y until it returns a disk appears ok was not modified. then type reboot.
4) you have not been allowing your computer to run its nightly maitenance scripts. your computer runs maitenance scripts every night at 3am... but if your machines is off or sleeping at 3am then these are not run. you can download cronathon or macjanitor to manually run these scripts.
5) your system is even more screwed up and you would benefit from runnning diskwarrior (commercial-ware @ v2.1.1 [at least for the next few weeks])
like i said i dont know your machine, but i can tell you from what you have mentioned that something is not working as it should be and you should fix this rather than assuming there is something wrong with osx or ical. im not a big fan of v1.0 of any iapp but the problems you mentioned are not due to apple's tendancy to release poor v1.0 apps.
for more details on disk maitenance or disk maitenance software titles and links check my website.
http://www.ambitiouslemon.com [go to the 'hints' section. there are also several thread here at MR where people have discussed these matters (use the search tool to find them) but these can be confusing since many people are not yet very familiar with osx and still have some very os9 thinking.