This question is in regards to SharePoint 2010. It would appear that when a page renders under a site using the uncustomized v4.master we get the following code:
<link rel="stylesheet" type="text/css" href="/_layouts/1033/styles/controls.css?rev=iaQ4I0LJDsWyKK5jS2ed3g%3D%3D"/>
<link rel="stylesheet" type="text/css" href="/_catalogs/theme/Themed/8411CE2A/controls-6E924A6.css?ctag=19"/>
<link rel="stylesheet" type="text/css" href="/_catalogs/theme/Themed/8411CE2A/search-7E1AFF02.css?ctag=19"/>
<link rel="stylesheet" type="text/css" href="/_catalogs/theme/Themed/8411CE2A/wiki-ECF524AA.css?ctag=19"/>
<link rel="stylesheet" type="text/css" href="/_styles/corev4.css"/>
Updating the Site's theme via Site Actions | Site Settings | Look and Feel | Site Theme doesn't appear to work any longer. While there are no errors presented, the actual change does not get reflected on the site. Other than that theme settings page showing the current theme as the newly selected one there is no visual change.
I suspect this has to do with that bottom line using the /_styles/corev4.css. Other sites (using the same v4.master) don't have this problem. And the code on those sites is as follows:
<link rel="stylesheet" type="text/css" href="/_layouts/1033/styles/controls.css?rev=iaQ4I0LJDsWyKK5jS2ed3g%3D%3D"/>
<link rel="stylesheet" type="text/css" href="/_catalogs/theme/Themed/8411CE2A/controls-6E924A6.css?ctag=12"/>
<link rel="stylesheet" type="text/css" href="/_catalogs/theme/Themed/8411CE2A/search-7E1AFF02.css?ctag=12"/>
<link rel="stylesheet" type="text/css" href="/_catalogs/theme/Themed/8411CE2A/wiki-ECF524AA.css?ctag=12"/>
<link rel="stylesheet" type="text/css" href="/_catalogs/theme/Themed/8411CE2A/corev4-8A0ABD2F.css?ctag=12"/>
Notice the difference? The bottom line appears to be using the CSS located in the auto-generated folder correctly.
Now for my question. How can I get the site back to using the auto-generated theme instead of that root corev4.css file found in the Hive? This is causing us to not be able to update our Site theme now.