Tom,
I’m sorry you’re seeing this problem. I’m afraid that JavaScript debugging is not available for Cocoa platforms. Unfortunately, MyEclipse 2013 does not run on a Carbon windowing system (as eclipse 3.8, on which it is based, does not support it).
The JS debugger is based on xulrunner technology that is unfortunately incompatible with Cocoa. We are working on a new JS debugger that will support more modern browsers, JavaScript and more efficient use cases/flows.
For now, the only workaround is to use an earlier release of MyEclipse (the 10.7.1 release is still available from our downloads page). This would have to be installed, clicking the Carbon 32 bit option during installation. You will also have to enable JS Debugging which isn’t enabled by default. It can be enabled by going to “MyEclipse Enterprise Workbench”->Preferences->General->Capabilities, clicking the Advanced button, opening the MyEclipse Professional Tools node and enabling the “JavaScript Debugging Support” option. Note that enabling this on MyEclipse 2013 will pop up a dialog when trying to use JS debugging, with a misleading message about the platforms on which the feature is supported.
Please let us know if this helps.