Xcode Archive; Organizer slow/not responding; pngcrush hogging cpu

Hello, sorry about the rather confusing title, but I tried to get in as much info as possible. 🙂

Problem:

1. I'm trying to archive my app into an ipa file for OTA testing (via TestFlightApp) - so in Xcode, I perform a Project > Archive.

2. After the archive is successful, it opens the Xcode Organizer to create the ipa file.

BUT as soon as Organizer is opened, Xcode becomes VERY slow & essentially unresponsive.

So naturally I open Activity Monitor to see what's going on and there's a process called "pngcrush" using up almost all my cpu (90%+) and causing Xcode process to be intermittently listed as "not responding". I can't seem to do anything in Organizer because it just keeps throwing the spinner/loading cursor.

Any ideas on how to fix this would be great!

Thank you!