I've just applied the latest update to New Blog Templates (2.1), and am having problems with the layout in Firefox:
1. The screenshots are displayed vertically rather than horizontally
2. The theme previewer overlay doesn't match the screenshot in height
3. The multi-domain dropdown box now appears at the bottom of the screen, rather than after the subdomain prefix.
The first two problems do not occur with the Twenty Thirteen theme, but do with WMPU Dev's Business Services theme.
The third problem occurs with both themes.
I haven't experienced any of the above problems with Google Chrome, either before or after the update.