Powerstore 3 won't let me edit or insert content

Have successfully installed Powerstore 3 and can add new products but can't edit any of the content managed pages. After I click edit, boxes appear with 'Page Name' and 'Content Area' which I'm able to change, but below that the gray frame is blank and won't allow me to type into it. I've tried all the editable pages that came with the site and they all behave the same. I've tried the admin area in Firefox and safari on a mac and ie8 and firefox on a pc. Any help would be appreciated.

Thanks Neil

Just tried adding a complete product listing (hadn't followed it all the way through yet) and the text fields for 'cart description' and 'short description' etc
are visible but you can't enter text or anything into them.

EDIT some time later
After looking at the source it looked as though the html editor FCK Editor was not loading correctly, so I tried uploading the HTML Editor files a fresh from the original
Powerstore download. Everything was fine until the uploads go to the JS files which seemed to upload again and again in an infinite loop. So I switched ftp client from
Filezilla to Dreamweaver and uploaded the offending files again. This seems to have fixed the problem.