Hi Jota, thanks for replying.
I have mapped the shop to a URL (instead of the IP) and done some other basic config. I recently updated it to 1.6.11 and that went without a hitch (but didn't resolve the issue unfortunately).
I have a theme (Leo Odin) installed and a number of modules. None of them concern URL rewrites, images or CMS pages though.
The issue ONLY occurs with images that I put on the CMS pages and upload via the file manager in the CMS editor. The product images all work fine, as does all other imagery on the front end.
Steps to reproduce:
Add an image in a CMS page. In this case "heroimg_charlotte.jpg".
Go check the CMS page in question. Image is displaying and shows the following code:
Refresh CMS page. Image no longer displays, replaced by white question mark
in blue box. Inspection of the page source reveals the following
img src="http://test.bybiehl.com/img/cms/1175x378xheroimg_charlotte.jpg.pagespeed.ic.Z9dsln9hgC.jpg" width="1175" height="378" pagespeed_url_hash="266613944" onload="pagespeed.CriticalImages.checkImageForCriticality(this);"
Following the URLs shows a 403 (forbidden) error.