Since I had this "Download Google Voice plugin" message when I try to make a call in Google Mail and I could not find any fixes posted here or on Google I thought I would leave a 2013 note. I went through all the installs for Google Talk and seemed like I could not get rid of this message. First of all, I could not find a Google Voice plugin to download except this one:googletalkpluginaccel.msi which I was told would fix the 1603 Google talk install error, which, I believe 1603 is just Google telling us that it is already installed. I don't know, but it worked for me. There are several other posts about this MSI out there and I will not address those here. Somehow this little gem fixed the error. Most of my problem came in the form of User Error. Me, that is not doing things in the proper order. I found out that I was trying to update the plugin while I was logged into Google talk first of all. The second thing I didn't do was plug in my camera and make sure all the devices Google talk uses are ready and working. These can be set by clicking on your Icon in the Chat window and doing settings for chat. DA! After logging back in to Chat and clicking the Phone Icon guess what? No message to download and I was able to make a call. So, you may be asking why am I writing this? Well I could not find a 2013 post for one thing and so I could not tell if the problem was ever fixed for Firefox 64. This is all on a Windows 7 64 machine with 6gps Sata USB 3.0 Diamond Radion ATI graphics 4 gb, Athlon II 455, 16 GB mem, ASRock Extreme III MoBo, Firefox 23.0.1. Thanks Mozilla for the great software allowing us to have a choice which is so hard to find these days.