Is Google chat disabled in Gmail if you use Adblock plus?

I have AdBlock on in Chrome on Windows and it works fine.

Go into the Adblock Plus options screen and update all your filter subscriptions, this should fix it.

Stackoverflow.com is a better site for questions like this.

I thought it was fascinating that Google could possibly deny usage of a product due to a third party plugin in a browser, i.e., Firefox.

I'm leaning towards the much more likely possibility that the confluence of browser variability, third party plugins, and a javascript chat client clashed in a bizarre way. I've never had an issue with gchat related to ad block. Although back to your central point, I don't see why Google couldn't deny any of their services based on browsers or add-ons, it's certainly not a new concept on the web.