debaric,
I know little about CO2 regulators for aquariums, but I know much about CO2 regulators for paintball.
What you're describing is a blown pressure seal. It's there to prevent damage to the system. These seals don't usually blow if the regulator was operating normally.
I suspect that the regulator is defective and will blow another seal, OR you may have blown the seal by opening the low pressure side too much.
Here's an easy way to blow one of those seals(there's more than one usually). You turn off the gas from the tank side. You then turn the regulator clockwise or counterclockwise thinking that you are "closing" the system. You were mistaken, and accidently opened the system all the way. You then replace the tank with a newly filled one, and open the gas from the tank side. The gauge blows on the low pressure, and so does the safety seal.
Either way you look at this, it'll be a lesson to be learned. It's either Milwaukee7's fault, or yours.
God luck on fixing it, and let us know what went wrong.