Freeze on double click in sub-extractor pattern

I've finally got reproducible steps on a freezing bug that's been bothering me for a while. I've attached a scrape to import into screen-scraper, then follow these steps:

1. Open the "Details Page" scrapeable file.
2. Select the "Sub-Extractor Patterns" tab on the sole extractor pattern.
3. On the first sub-pattern, double click in the white space next to the ADDRESS token in the first line, after the br tag.

Results: Screen-scraper freezes and I have to use Task Manager to kill it. I've lost work a couple of times doing this by accident while trying to open a token dialog.

I'm using Enterprise 5.0.11a on Windows 7.