OSCLASS: Bender Black theme drop down distortion in item-post.php

I noticed that there was a distortion in the dropdown menus in the new ad post page (item-post.php).  Used Firefox's "inspect element" to investigate initially, and found duplicate "select a category" entries getting populated though only one is actually displayed.

It looks like this:
The category dropdown and even locations dropdown seems to expand.

At first I thought my theme's (Bender_Black) CSS for messed up. So I re-uploaded my local main.css backup but the problem was still there.

Then I thought this might be an issue from some plugins. And voila!  It was.
After disabling suspected plugins one by one, I found the plugin causing the problem - "Rich edit" plugin. After disabling the "Rich Edit" plugin from Admin Dashboard > Plugins > Manage Plugins, the issue is gone.

When downloading the plugin, I did not get any compatibility issue notice.

Hope it helps some one facing similar issues.
Ps: I did not check this issue with other themes.