If you're suddenly seeing ads in YouTube videos or on Pandora.com, it may be a bug in Chrome. According to a post in the EasyList forum, a confirmed bug in Chrome is causing the YouTube and Pandora Chrome apps to be treated as a browser extension, which ad blockers ignore. This affects all ad blockers, not just AdBlock.
The workaround is to remove the apps from Chrome. You don't need the apps to watch YouTube videos or to listen to music on Pandora. You can safely remove them permanently, or just until Google releases an update to Chrome that fixes the bug.
- Type chrome://apps in the address bar or click the Apps icon in the bookmarks bar.
- Right-click the app and select Remove from Chrome.
If you're on a Chromebook, follow these instructions instead to remove an app or extension.
Clarification: In this context, the Pandora and YouTube "apps" are the Chrome browser apps, not apps on your mobile device or applications on your desktop.
Note: The Pandora app is no longer available in the Chrome Web Store, so here's the direct link you'll need when you want to reinstall it: https://goo.gl/94wEn
If you've tried this and you're still seeing ads on YouTube.com, please see this Knowledge Base article for more suggestions: I'm seeing ads in YouTube videos
Update May 8, 2016:
This issue seemed to have been fixed, based on the relatively few reports we were getting. Like the evil spirits in the movie Poltergeist, it's baaaaa-aaaack. It looks as if the YouTube app is installed automatically with Chrome (either a new installation or an upgrade). So if you're seeing YouTube ads again and you thought you removed the app, check chrome://apps. You may have to exorcise...that is, remove it...again.
Note: If the screen is black but you hear audio in YouTube videos, please see this Knowledge Base article: YouTube videos show a black screen but I hear the audio