missing detail in stacktrace

My first Geb script (intro.groovy, below) fails (below) without enough detail to fix it. The stack trace just says line number 8, the Browser.drive() line, but the script gets past that because I can see it input "wikipedia" in the query field. So, I need to know where it's failing inside the closure.

I'm using Groovy 1.7.4 and Firefox 3.6.12 on Mac OS 10.6.4 and Apple's Java Update 3 (1.6.0_22).

Also, I'd like an option to not close its Firefox, so I can examine what the script is failing on. On the other hand, for a test suite, I'd like an option to take a screen-shot of the Firefox window and a dump of its content files (HTML, CSS, JS, images, etc) at the point where each test script fails.