Programmers and Opera 11.10

When I view Programmers site in Opera 11.10, the following error message is displayed on each page:

Error message when viewing Programmers site in Opera 11.10
No registered application for this type of extension.

I posted a bug report. The behavior is not reproducible by the developers. Later I updated the question with more details about what causes this error message to appear.

Does anyone get this erorr message?