Hi,
Please test if you can open it in Safe Mode:
Press Win + R and type “outlook.exe /safe” in the blank box, then press Enter.
If there’s no problem in Safe Mode, disable the suspicious add-ins to verify which add-ins caused this issue.
Apart from signatures, what other buttons can't you use? It would be preferred if you could provide a screenshot of the section and the buttons. You may upload the screenshot to SkyDrive and share it via a link:https://skydrive.live.com/
Regards
Melon Chen
TechNet Community Support
