If this is like me it was probably an Opera web browser notification. I couldn't figure for the life of me wth it was. So i started killing programs in the task manager and it went away when i killed 2 Opera tasks (updated or something). It happened on 2 complete separate computers with very little in common.
I'd guess it was an Opera update message that gets hung up or errors. But after opening Opera i did see it was updated. Who knows for sure though. Posting this for future people trying to find this solution.