removing other calendars
I had a similar issue and was able to correct it fairly easily. Before i went to the iphone i used a Palm device which used PocketMirror conduits to sync with Outlook on my pc. This created 4 additional calendars.
To remove these additional calendars i had to go to my "Folders List" in Outlook 2007, find the additional calendars, and right-click-delete. My calendars were actually grouped under a folder named "PocketMirror", so i deleted this entire folder. I waited about 30 seconds and the calendars disappeared from my iPhone after it did a sync.
Hope that helps!