Steps to replicate the issue:

• Enable "Show preview without reloading the page" in Preferences
• Start editing a template or module
• Enter a page name in the textbox below "Preview page with this template"
• Press Enter/Return

What happens?:
The edit is submitted (saved if modified).

What should have happened instead?:
Live preview.

Other information:
Not reproducible with safemode=1, I may have jumped the gun. Still the handler not attached to the <input> element itself is potentially an issue.