I just tried creating a zip file and it seems to have an extra folder at the top level.
I have added in some more files (libs) to my addon but didn't expect this to cause problems. Has anyone seen this before?
It might help if you mentioned what the "extra folder" was called, and how you're creating the zip file (eg. built-in Windows function, third-party utility like WinZIP, or generated by WoWI itself from an SVN repository).