I had this same issue. I am running PMS 1.72.0 on Windows 7 (64bit) I have the latest version of Java installed. When I run PMS a message pops up and says "PMS uses Java Runtime 7.0, it will now be downloaded and installed". It goes away for a bit then comes back with an error (which I forgot what it says but in essence it can't download Java and exits and PMS never runs). This seems to happen after a new version of Java comes out. The fix is to re-download Java from http://www.java.com
and reinstall it. Regardless if you have the latest version or not. When Java installs it will remove the current install (regardless if it is the latest version or not) and install the current version. After I do that PMS runs fine. I suspect when the next release of Java 7 comes out this issue will pop up again.