Forum Editor doesn't accept paste

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.

The only way to get something from the clipboard into the Editor is throug the "Edit HTML Source"-Icon and pasting the text in that separate HTML-Source-Editor.