W3 causes website to display only gibberish

Hi,

Not sure what happened and I reckon it must be due to some recent update, but W3 now causes my website (www.planetcompliance.com) to display only gibberish, i.e. ???r?F?(?[??;??W”?u???^?\l??d?h and so on

When I hit reload the page usually displays properly, but obviously not perfect. It works fine if I deactivate the plugin, but that slows down the website.

Any thoughts?

Many thanks!
Jochen