Serialization fails, because the call to [code]infinitescroll.init.js.php?p=$pathInfo[/code] is not properly sanitized before load. There is a '+' char in the string, which gets translated to a ' ' by the browser.
Before handing it to the browser it needs to go through 'urlencode'.
Once I did that, it worked! No need to urldecode it, since that is already taken care of by the browser loading the URL.
Using InfScroll WP Plugin: 2.0b2.121120.