Windows 7, Lyx, third mouse button, paste

[Oliver Frost]

Hi folks,
I'm using Windows 7 and Lyx 2.12. My problem is: Anytime I click the third 
mouse button in Lyx, Lyx pastes the previously selected text into the document 
where the cursor is at that point. This is terribly annoying. Does anyone know 
how to disable it?
Thank you very much!
Best regards Oliver