Well, I have tried all of the suggested fixes. Upgraded to iTunes 7.3.1, confirmed iTunes add-in. etc. And problem still exists. Seems like it is an Outlook 2007 issue. Interestingly, if I right click on appointments in Outlook, the ones created on iPhone dont offer a menu but the ones created in Outlook do. Double clicking on either works. So clearly, there is some, apparently hidden, attribute of Outlook 2007 created appointments that doesnt play nice with iPhone or iTunes or something.
A workaround posted on another board by another user works for me. It's a bit annoying but it is the best thing I have seen. Following is their suggestion for anyone in the same boat as I am in.
My workaround
copy, paste, and modify an iPhone-created appointment that was synced over to Outlook, and use it for all future Outlook-created appointments. Tedious, but it works (and obviously iPhone then recognizes the store/code/tag in the new Outlook-created appointment.)
Any other suggestions are welcomed and appreciated.