With my configuration here (Internet Explorer 6.0.2900.2180) the forum editor doesn't accept
Ctrl+V nor the Icon "Paste as Plain Text". Nothing happens.
With the same configuration other forums (like Yahoo-E-Mail) work fine to paste something.
What are you attempting to paste in? Text seems to be working fine for me (in the simple tests that I just did) with both <Ctrl>V and right-click Paste. Are you sure that focus is in the editor part (and not another item in the editor)?
I just tried it again in this forum edit. It doesn't work.
I tried to copy simple text from notepad into the editor.
The cursor is blinking and i just clicked inside the editor window. I think, there is some security option of IE 6 which denies the paste. I will try the same on a different system to test it. But it still strange on this system.