A hotfix (a TAR of files to upload) have been uploaded to this issue. These files are made to the latest intra-version state (i.e. may roll in earlier fixes too if made to the same files) - so only upload files newer than what you have already. Always take backups of files you are replacing or keep a copy of the manual installer for your version, and only apply fixes you need. These hotfixes are not necessarily reliable or well supported. Not sure how to extract TAR files to your Windows computer? Try 7-zip (http://www.7-zip.org/).
However, I noticed that the theme I was generating from, "default2", was actually slightly broken. So instead I sent all custom templates over to default and modified the custom css file so it kept almost everything from original default css (specifically the equations) with the exception of a couple modifications. Doing this and then generating themes from default instead of default 2 not only resolved this issue, but color schemes are more accurate and it looks a tad cleaner.
Some theme images are not generating when you save a new theme. Additionally there may be a problem with the colour selector.
However, I noticed that the theme I was generating from, "default2", was actually slightly broken. So instead I sent all custom templates over to default and modified the custom css file so it kept almost everything from original default css (specifically the equations) with the exception of a couple modifications. Doing this and then generating themes from default instead of default 2 not only resolved this issue, but color schemes are more accurate and it looks a tad cleaner.