In order to use colons or dots in urls of your settings or data files, you must use relative urls (with http://) In other case, you will get "error loading file" message. This problem is caused by flash player, not amCharts. So, instead of:

so.addVariable("settings_file", "settings.php?time=22:00");

you should have:

so.addVariable("settings_file", http://www.yourdomain.com/settings.php?time=22:00);

However you must also know, that using relative paths in some cases can also cause problems. So the best solution would be not to use colons or dots in urls - replace them with some other symbols if you can.