I discovered that this is a bug and I think it occurred as a result of a change in how parse_ini_file works with PHP 5.3: All values that contain a space in the ini file must be double quoted.
What is occurring is your easyphp.ini file is being read by another config file (i think i18n.inc.php) with parse_ini_file and it is coming to the last line which contains your PHP install directory (or something like that, not exactly sure). Because the directory contains a space (most likely because of "Program Files" it needs to be enclosed in double quotes. However, it is not and you (and everyone else) are getting an error. To fix this if you care to, place double quotes around the value after the = and at the end so that it looks like this:
OldRunningPath="C:\Program Files (x86)\EasyPHP5.3.0\"