Same here Seems the sig key has changed, so I went to http://www.google.com/linuxrepositories/ but it's the same old key.
I had a few isolated instances of that. I remember fixing it as follows:- sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com A040830F7FAC5991 Where the numerals are the ones shown next to Badsig. BTW. what is the red hat --nogpgcheck equivalent for Ubuntu ? I can't remember - getting old.
best solution what i did in past is i remove the repo and installed it form google chrome site .deb package and right click and install it auto add it to repositories hope it work for you too
and http://askubuntu.com/questions/1877/what-is-the-easiest-way-to-resolve-apt-get-badsig-gpg-errors but I'm going to wait and see. See http://googlechromereleases.blogspot.com/ for the new Chrome stable!
And it's fixed. Downloading the new Chrome now. Edit: Need to get 29.2 MB of archives. After this operation, 1,327 kB disk space will be freed. Looks like they're serious about reducing bloat in their code, an intention they had announced a while ago!