Clicking document icon presents grey screen where document should be.
This issue is described on Google’s forums:
Google Docs Viewer does not work inside iframe (embedded mode) when the Google login session is partially signed-out (which probably occurs due to session time-out)
In my case, if I access Gmail in a new tab and either sign out completely, or sign in completely, the problem goes away. So not a major bug…
@jaemaz, I tried the scenario of partially signed-out as described by the person who had reported issue on Google’s forum in Firefox on Ubuntu and is working fine. Can you tell that how exactly you partially signed-out so that we can reproduce this issue on our end.