Steps to reproduce:
Click on StackOverflow icon
Click on popular tab
Click to sort by votes
Click to show all time
I could manually reproduce that every time I tried.
The following is a print screen of the message shown after going through the steps:
And if I subsequently do a F5 refresh, it works.
And considering the fact that I clicked on all time option, it makes me think that what happened, actually, was a timeout.
If my guess is right, I think that timeouts are currently being handled elsewhere differently. So, while resolving the performance issue (therefore, avoiding the timeout), a proper timeout message and a link to refresh the page would be a perfect fallback.
Note that it might not related to timeout - it was just a guess on the issue - it could, for example, be some weird caching problem due to current alpha testing. Anyway, it still seems to be a bug.