If RainRGB is not running at all, then I would have to ask first if the .exe file exists in the path you are calling it from? Based on your post, that would likely be C:\Program Files\Rainmeter\Addons\RainRGB\RainRGB.exe. Is the file actually there?
Assuming it is, is there actually a file called Variables.inc in the same folder as your skin .ini file? Does it have a [Variables] section in it, and does that section contain a line
First things first. Let me know if RainRGB.exe is actually in the right place. If so, please just zip up your entire skin folder (WorldClock2), host it on http://mediafire.com, and put the link to it in your reply. Then I can take a look and see what might be going on.