It wasn't ON my birthday, but at the end of my birthday week celebration. My best friend of a decade worked for a timeshare company and got us a week in a beautiful two-bedroom condo in Orlando (where we lived at the time) for a staycation. We had different friends and family members come and go, did lots of activities, just a wonderful time. Then near the end of the week, she completely lost her mind for reasons I still don't understand, totally flipped out shrieking at me, and ended our friendship.
Most of my memories from that week are fantastic, but it's been a few years now and I still have no clue what I supposedly did to her.