ok - did that...
Renaming the templates did nothing - the system still locked up. (I had to do dwt.php instead of php.dwt or the templates wouldn't show up in the dropdown.)
Turning off the preview allows me to proceed but at a major cost. Without being able to see what the various options do is like being told I can drive my car but only if I cover up the windshield when I do so.
It sounds like what you're telling me I have to do is turn the preview on, don't select a template and run through the wizard to see what the various options provide. Then, after I figure out what I want and have them written down, I have to exit the wizard, turn preview off, then go back in and run the wizard with my choices and my template selected. Then, since I'm assuming these preferences affect all of the Web Assist extensions, I am going to have to turn preview back on in order to preview anything when I run something else of yours.
If that's the case, that's unacceptable.