First of all, when I try to type the screen of the editor goes light blue and I can't see what I typed till I stopped typing.
Secondly, the right links for paraghrafs are so small that I can't read, and only one dropdown opens the containers the classes doesn't work nor even open...
It seems like some JS libraries are not loaded.
First of all check examples provided with original script. are they work well?
Then check JavaScript console for errors. If you can provide an url where you use wymeditor I can check them for you.
Coding this doctype any problem with ie7:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">