I have a javascript web site that is simply hanging in konqueror, and I'd like to figure out why it's not loading/running properly. The same site works in latest FF and Chrome, but in konqueror with KHTML, it doesn't load at all and with webkit it loads partially but doesn't completely load/start running, but the js debug window never seems to pop up.

Any ideas on how to investigate further?

I've already enabled the debugger and report error - both check boxes are on, but I now can't find the debugger screen itself.

Thanks,

When using the webkit view mode, to open the web/javascript console, you can right-click anywhere and select Inspect from the drop-down. Konqueror will open the web console in a separate window. You might also try installing other qt webkit browsers (inc. rekonq, arora, qupzilla), in particular rekonq works nicely and is well supported. These other browsers open the web console in-window. From my observations all browsers that use qt's webkit operate very similarly (and sub-par compared to the likes of the standard set: FF, Chrome, etc. though my hopes are up for improvements with Qt WebEngine based browsers).
I would suggest that it isn't worth investing in getting your site to work with konqueror's KHTML backend as it seems to have been left to the wayside. It may not be completely abandoned, but there is a lot of recent additions to javascript that it hasn't implemented.