It's clear that Hulu and Crackle are using videos streamed over protocol of RTMPE. It is defined as a security protocol for protecting vids from downloading with most video download software. For downloading videos from Hulu, I also tried streamtransport, it really works with Hulu as stated.
But I want to recommend your guys more appropriate desktop software, which combines features to
record rtmp stream, record PC screen video and download common online videos. It provides you multiple solutions to
capture Hulu videos from screen or directly download them. It also works with Crack.com and many other sites using rtmp protocol.