Apple Snow Leopard Freezing Installs

I have been having an annoying problem with my 27" iMac for a couple of weeks now. Every time I tried to install a 3rd party application it would hang or freeze on "Preparing" install. I tried Apple support and also wasted time digging through the web. What was the cause of this annoying problem? The iPhone Simulator. I have found that if you have the iPhone Simulator running in the background, 3rd party installs will fail every single time. Quit the Simulator and all the sudden installs work again.