Sorry, I wasn't clear in the op, You need to extract the file via computer then put the theme (flyin etc.) in you AndroidThemes file on your sd, then in mm choose "pick existing theme" then click on flyin flolder then flyin.xml. Not sure what is happening but it should work fine. First off, I zipped the folders in my AndroidThemes folder via root explorer, (shouldv'e used 7zip) then uploaded to my dropbox account. When I unzip the files there is an extra folder that should not be there, so since there is enough interest in this I am now going to zip the files properly and update the op, then everything should run smoother.
P.S. I have used mm for a very long time and I never extract the files via mm cause it always gives me errors too. I have always just extracted via computer or root explorer then move the extracted folder to AndroidThemes on MM. Alot, of people knock mm, but I love it cause I don't have to wait on someone to update the theme etc. , I just change .pngs .xmls within my themes in AndroidThemes then apply, no need to wait. Do it yourself gets things done faster in my experience.