Piwik Row Evolution hangs - waits forever - problem (no replies)

Greetings,

I never saw row evolution work until accessing demo on piwik site (thanks for that!).

In our installation, clicking on row evolution has a pop dialog which displays "Loading Row Evolution"
with a timer icon...but it never goes away.

There is also no activity on database and the logs do not print any messages.

I thought i had found a page that recommended clearing cache, restarting server, and possibly upgrading.

I tried clearing cache and restarting server with no change and we are already using latest version (v1.11.1)

We are looking at Piwik as a key part of our web analytics, but unless can get "simple" problems like this resolved may have to
double down on Google Analytics.

Thanks for any assistance.

Regards,

-tony