events don't change

new problem with iCal. when i change an event, both events stay. there is some poor interaction with iCal as well. if i set an event and then drag and drop it to another date, both stay there. if i delete, it comes right back, usually when i go to another month or when i use iSync.

i have tried resetting the sync history many times through iSync and have also tried getting rid of the calendar cache, also many times. i have tried sync to replace all data on mobile me from my computer after i tuned the calendar (didn't help, they just came back as dups) and i tried it just the opposite way, replacing all info on the computer from mobileme.

any suggestions?