I am using TubePress 3.0.1 on a WP 3.5.1 installation on a shared linux server (PHP 5.2). I am having exactly the same thumbnails issue.
The videos and thumbnails display great for both YouTube and Vimeo, and the first video runs without issue. The thumbnails either do not load videos or simply fade out the video box (depending on the browser). I am thinking that this issue is due to the Cross Domain Ajax issue as my Site and WordPress URL are both set to https://www.worldnewsreader.com but the tubepress documentation indicates that the ajax call is most likely to worldnewsreader.com. I am fairly versatile with manipulating my .htaccess file but I still can’t seem to get the thumbnails to load properly. Firebug hasn’t helped to fix the issue either.
I’ve deactivated all the existing plugins to better isolate troubleshooting this issue, and you can view the tubepress installation at https://www.worldnewsreader.com/trendingnow. I’d greatly appreciate if you can provide the necessary mod rewrite to insert into my .htaccess file so that I can get the thumbnails to load properly or if there is a better way to resolve this issue. Thanks.
jcarrier