This issue is marked resolved, but there actually are serious problems associated with what ksemel reported when bwp-minify is used with various common server configurations. I have only spent a short time testing, reading the code, and identifying problems, but this is what I have found so far.
bwp-minify's path-guessing fails under Windows, works with dedicated host serving under Linux, but fails with common virtual host serving configurations under Linux. Those problems are due in part to $_SERVER['SUBDOMAIN_DOCUMENT_ROOT'] containing a static path set in an Apache config file, rather than a valid path to an individual virtual host document root. There also is a malfunction associated with the use of @parse_url($minurl) that I haven't fully-determined yet.
Additionally the default empty string setting of $min_documentRoot in the min config.php is not valid with virtual host web serving, because it causes $_SERVER['DOCUMENT_ROOT'] to be used, which isn't reliable for the reason explained above. The solution is to set $min_documentRoot as shown below, which I have found works reliably with both dedicated and virtual hosting under both Windows and Linux:
$min_documentRoot = substr($_SERVER['SCRIPT_FILENAME'], 0, -strlen($_SERVER['SCRIPT_NAME']));