I have seen this a few updates ago and thoughtt it might get fixed. When an update is installed, the pinned taskbar icon does not work on the updated version. I wish I caught the error, but it specifically talks about "parameter" errors. If you can not reproduce it, I will grab it next update. The workaround is just to unpin the icon, open the application and re-pin it.
1Password Version: 1Password 6.0.183d
Extension Version: Not Provided
OS Version: Windows 7 x64
Sync Type: 1PW Families