We have learned recently that there is an issue with an upcoming version of Chrome that will cause components of Sitecore to stop working as intended. This will only affect clients on versions less than Sitecore 7.1 using Chrome version 37 or higher. The impact is that Sitecore popup dialogs stop working, blocking users from accessing certain screens in Sitecore.
There is a hot fix for the issue, but the exact fix is unique to the build of Sitecore you are running. Sitecore support was able to give us specific updates for a particular release of Sitecore.
There is now a knowledge base article about the issue on Sitecore’s site, as well as a consistent fix that is more easily applied: