It means either phpinfo() wasn't reporting memory_limit on your server or the parser for the HTML that phpinfo() dumps failed. I'm inclined to believe the later as the error message didn't give you a specific memory value as it should. Unfortunately, phpinfo() doesn't spit out an easy machine readable format so I have to parse the result to get info about the PHP environment. I've made modifications to the installer so that it only fails the memory check if it explicitly finds an amount lower than 12M.