That looks like someone changed the command window from a Window_Command to a Window_HorzCommand.
The simplest answer would be to redownload the plugin, as that certainly doesn't happen on the stock version. If you still have the problem after that, then one of your other plugins is overwriting the function that draws that window. You'll have to figure out which one it is on your own, by disabling plugins one by one until the problem goes away. Of course, the process of narrowing down which plugin is causing the problem is a lot faster if you just recently added new patches or plugins, the culprit is likely one of those.
Things like this don't just happen. Something actively has to be done to change something like that.