OK, just had a look at this error on a server I'm working on, this has safe mode off but an openbasedir restriction in effect, allow_url_fopen is on and gives the error above.
Debugging the code the reveals contents returned from file_get_contents are null, hence the error.
If I manually dial up the url in question
http://modx.com/extras/download/?id=4d737199f245546023000014 after a redirect to amazon it works, ie I can down load the zip file so its not that.
OK, change the code to force CURL to do this, fails unless you add the line :-
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
to allow for the redirect, it then still fails with this :-
PHP warning: curl_setopt() [<a href='function.curl-setopt'>function.curl-setopt</a>]:
CURLOPT_FOLLOWLOCATION cannot be activated when safe_mode is enabled or an open_basedir is set
Forcing fsockopen also fails.
This used to work on this site so I'm guessing the fault is the redirect to Amazon for the package, it doesn't look as though this is going to work on servers with open basedir restrictions in effect at the mo.
Can we have another provider url that acts as a package mirror that's not in the 'cloud' for these servers, i.e as it used to be, either that or can someone come up with some cunning code to get round this.