Hmm, having just done some test runs of myself now, I am intrigued by what may be the problem for others. Here's a little visual readme for those in a spot of bother.
The first file shows a screengrab of my
WoW C drive directory. I have highlighted the files from the WoWME download folder that should be visible when exported to the main level of C:\World of Warcraft and how to set out your wowme.cfg file. The second file is a screengrab of the Data folder, showing the MPQ's I have stored there and the correlation between that and the .cfg item.
To re-iterate:
- Once you have added any MPQ's you want, arranged the WoWME items as required, edited the wowme.cfg document, then and only then do you activate the application WoWME.exe
- This should load
WoW as usual after a short delay. If you hit a WoWError pop-up, you've done something wrong either with these steps for the program, or the MPQ itself
- When
WoW loads up and hits the log-in screen, press F8 on your keyboard before entering password and logging in
- If you hit an error after this, it's probably a conflict between the patched version of
WoW on your PC and the patch level for WoWME or the server you are connecting to
To be perfectly certain you get the right results, I have directly uploaded the most recent .rar file for WoWME to this thread.
That's about the best I can offer. If you still have trouble, then a

is all I can offer.
Regards,
Xerxes
EDIT:
Another point to add, the MPQ file extension. I think the official Blizz MPQ's have .MPQ in upper case, so if you follow "####.MPQ" convention as your filenames, then add "####.MPQ" to the .cfg file, it should match up perfectly and work in your favour.