my case is a bit different, i have a mashup and potentially a more complex folder structure, i hope that if it is caused by that bug it will be fixed. i can't shot at my file like a sniper .
my guess is if the content of wbfolder.wbl can affect the uploading of the mashup/extension?
moreover in the article i have link i read "If the name of an extension already exists (or occurs more than once in the zip file), the zip file is not uploaded." what it means the name occurs more than once in the zip file??