The updater script I wrote for the portable build of Google Chrome periodically runs into exactly the same issue.
The 'LAUNCH' script is written to check this webpage when it's run. This webpage gives the current stable release number, and is used to then trigger the 'Updater' script if the version given doesn't match the 'Last Version' file in Chrome's profile.
This 'tweak' was courtesy of Forum member baraka. Normally, it's reliable, and works without issue.
On occasion, there is a problem at Google's end where the current stable release is not actually in the repo. Either that, or the 'current' release number isn't correctly forwarded to the above-mentioned webpage. Not only does the script not download anything - so the 'chrome' directory doesn't get replaced - it then leads to a 'loop' situation where the browser keeps asking you to update, every time the browser is launched.
It's annoying, but there's not a whole lot any of us can do about it. Myself, I think a good part of the problem is the highly-automated production pipeline Google have set up at the Chromium Project, where the only real human interaction is the supply of 'fixes' & 'patches' sent in by all those developers, world-wide, who are regular contributors to the project.....but even these are then automatically 'slip-streamed' into the source code files as and when they are received at the Project (it's from here that Google periodically draw the source code for the next stable build as & when it materialises). The project has a whole fleet of semi-autonomous 'bots' that do nothing BUT create build after build, 24/7, as and when 'fixes' come in, without the need for human intervention.
There appears to be very little in the way of a real-time overview to the whole process. So, occasional glitches like this are bound to sneak through.
Mike. 
getting latest chrome is more simple using the "direct" link "google-chrome-stable_current" from google itself 