Line 46 is using the parse_url function on the REQUEST_URL server variable. However, REQUEST_URI apparently doesn't work on IIS servers. I can see you are running IIS (from your error message).
I just had the same problem after upgrading Plogger. I found a solution on this blog: http://davidwalsh.name/iis-php-server-request_uri
Basically, I used his code and pasted it near the top of plogger.php. The error message is now gone!