WordPress 3.4.2 was just released, as a security and bug fix release.
Andrew Nacin had this to say about the release.
- Fix some issues with older browsers in the administration area.
- Fix an issue where a theme may not preview correctly, or its screenshot may not be displayed.
- Improve plugin compatibility with the visual editor.
- Address pagination problems with some category permalink structures.
- Avoid errors with both oEmbed providers and trackbacks.
- Prevent improperly sized header images from being uploaded.
One issue in particular that was affecting my development was #21106, so I’m thankful that was fixed.
You should always keep up to date with new WordPress releases, so as soon as you can, go update your WordPress site(s).