I have seen people report this before here, so it might be related. If you are certain that this bar appeared after installing Messenger Plus! with the sponsor program, and seeing you already followed the instructions in the sticky post, you could try the following:
- Reinstall Messenger Plus! with the sponsor program
- Reboot your computer
- Uninstall Messenger Plus! right away (following these instructions)
- Reboot
See if it's gone. If so, you can reinstall Messenger Plus! without the sponsor program. If not, tell us.