When I try to start chrome I get a message that says "Failed to load extension from: .Manifest file is missing or unreadable"

After finally fixed it by deleting all the .desktop entries for chrome.

find ~ -name "*chrome*.desktop"
#and then after looking at the list and maybe looking inside the files and deciding
#that you are ok with deleting them just to see if this fixes it....
find ~ -name "*chrome*.desktop" | xargs rm
#or something like
find ~ -name "*chrome*.desktop" | xargs gvfs-trash
#or maybe just save them in a folder or rename them while you make sure
#this is the problem

I can't reproduce the situation so I can't tell you for sure if this was it, but it might be worth a shot if you have the same problem.

Had the same problem. This is how I fixed it:

apt-get remove google-chrome-stable
export CHROME_VERSION="google-chrome-stable"
wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add - 
echo "deb http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google-chrome.list
apt-get update -qqy
apt-get -qqy install ${CHROME_VERSION:-google-chrome-stable}
rm /etc/apt/sources.list.d/google-chrome.list
rm -rf /var/lib/apt/lists/* /var/cache/apt/*

I ran into this problem as a result of an incompletely installed extension. The extension, chromium-lwn4chrome, was installed through aptitude. I've got no idea how some of its files ended up not being installed.

I finally found it by running

strace -ochromium.strace chromium

In the chromium.strace file, I searched for the string "anifest" and found the lines

 lstat("/usr/share/chromium/extensions/lwn4chrome", 0x7ffd0c3bc520) = -1 ENOENT (No such file or directory)
 access("manifest.json", F_OK) = -1 ENOENT (No such file or directory)

Searching for lwn4chrome, I found

 open("/etc/chromium.d/lwn4chrome", O_RDONLY) = 3

Investigating that file, I found

export CHROMIUM_FLAGS="$CHROMIUM_FLAGS --load-extension=/usr/share/chromium/extensions/lwn4chrome"

but there was no file or directory named /usr/share/chromium/extensions/lwn4chrome on my system. I purged the chromium-lwn4chrome package, and the problem went away. I then reinstalled it (because I was curious) and this time everything worked.