JQuery UI, ThemeRoller and transparent datepicker

Recently we had some issues with JQuery UI which didn't render the widgets correctly.

An example of a JQuery UI widget is the datepicker (screenshot), like you can see working on Apex Blogs

If you want to change the look and feel of the date picker (or any other widget) you can do that by creating a new theme on the ThemeRoller site or by selecting one of the gallery.

However while we did that our datepicker became transparent and it looked like it couldn't find the css or the background images anymore. As we already used it in more projects, we were sure our code was right.

Finally we found that a different version of the JQuery UI can get you into that situation. The fix then is to use the version you know your css works with or to download the latest version of JQuery UI and create the theme again from the site and use that instead.