Whoa! Thats not supposed to happen!
While I strongly recommed you create a bug report at bugreport.apple.com (attaching a System Profile report and the project you were opening that causes the panic), perhaps we can help you get functional again.
• Have you done all the usual "Is my Mac OK?" stuff, like run Disk Utility, run Software Update to get the latest versions of everything, check for viruses & trojan horses, etc.? (In particular, iAd Producer 4.0.1 was recently posted, so you should ensure you're running the latest version.)
• If you hold down the shift key when you launch iAd Producer (to prevent opening previous documents), does your machine still panic? (If so, attach the problematic projects to your bug report.)
• If the shift key doesn't prevent the panic, try removing com.apple.iAdProducer.plist from your home directory's Library/Preferences folder.
• If it appears to be related to one particular project, do you remember what type of content it has in it?
And when you do write up that bug report, answer the questions above, and attach the System Profile report and the problematic projects. (Apple engineers always ask me for that stuff, so I've learned to provide it up front.)