I have several wp sites and have recently upgraded most to the latest version. All was working fine with themes a couple of days ago but today I am having the same error as everyone above. Tried reinstalling WP but no joy.
I can manually upload-install-activate themes but can’t search and use ones via WP. The search options don’t even appear when you click on Add New Theme – Clicking on Featured – New and Recently Updated also doesn’t work.
Thanks for logging the trac error mrmist hopefully they fix it soon.