I want to use Google voice and video chat on Iceweasel 10.0.4 on Debian Linux 6.0.5. (Iceweasel is the Firefox derivative that comes with Debian Linux.) I've installed Google's voice-and-video Web-browser plugin package. It actually includes two browser plugins: "Google Talk Plugin" and "Google Talk Plugin Video Accelerator".
I don't need video chat. So I've used Firefox's add-ons manager to disable the Video Accelerator plugin [edit: I didn't know it's a mistake to disable it].
When I try to voice-chat with a contact, I get the error message: "Click here to add voice/video chat."
When I try to call a telephone from within Gmail, I get the error message: "Please download the voice plugin to make a call."
When I go to Settings > Chat, as the "I'm unable to make or receive phone calls in Gmail" troubleshooter recommends, I don't see any version information. I just see: "Gmail voice and video uses Flash for video rendering. Install Now".
Why am I getting these error messages?