CiviEvent registration & IATS payment processing fails to blank page
1.5.3 (see info.xml) file is a release for CiviCRM 4.4 - 4.6

If you're on 4.7 - you can try our pre-release master branch - I just checked and Event registrations are processing fine w/ iATS

Though what you're seeing may actually be a server configuration issue... or a issue w/ your specific CiviCRM instance;