Improperly signed update.

I know there are already about 100 questions on this, but in general they are specific to each person.

My problem, in a nutshell is that when I try to update Sparkle tells me improperly signed update.

Here's what I do:
1. Open up terminal and do 'ruby "Extras/Signing Tools/generate_keys.rb"' (without single quotes)
2. Add dsa_pub.pem to Xcode Project and add relevant key and value to info.plist.
3. Build app and zip it up.
4. Back to terminal and do 'ruby "Extras/Signing Tools/sign_update.rb" \ ~/Desktop/app.zip ~/Desktop/dsa_priv.pem'
5. Add returned string to update

I then go into an older version of my app, try and update but get 'Improperly signed update'.
It's important to note I've started this whole process from scratch 3 times and have always had the problem of the 'Improperly signed update' error.

Here's my update feed: http://squaredtiki.com/idzr/idzr-app-updates.xml

The only thing that did look slightly odd in my feed compared to the example feed, is that the signature is much longer but I'm unsure whether or not this is a problem.