When changing project, version validation always fails

While confirming http://drupal.org/node/185851 I noticed another bug. When you change an issue's project, and the version choices are updated via JS, when you go to preview or submit your comment, the validation on the version field fails with: "You have to specify a valid version." and the version selector is reset to <none>, even if you had previously selected something reasonable from the list updated by JS.