The behaviour of copy and past in PuTTY is different than in Ubuntu. With PuTTY under Windows I never had a problem how to copy and paste, but under Ubuntu I am always confused. That is why I wanted to write it down. For me, but also for you of course.
Coping from PuTTY
Select the text with the left mouse button and paste with the middle mouse button.
Paste in PuTTY
Select the text you want to paste. Paste in PuTTY with the middle mouse button.