@xinfo: thank you for notices.
1. Gzip. It seems WordPress gzip (or gzip of any other plugin) conflicts with Web Optimizer's one. So you need to use Gzip for HTML (CSS and JS files can be served via Web Optimizer w/o any issues) in only one place. It can be WordPress, cache plugins, or Web Optimizer itself. It's not the issue (but there was added a text about gzip disable in installation instructions, such text is on Troubleshooter page).
2. Website w/o images. There was a bug with wo.static.php file (proxying images' caching for your website), it wasn't copied to cache folder. It has been fixed. You can download the last version (0.6.1.4) of Web Optimizer plugin and deactivate/activate it or just copy this file (wo.static.php) from web-optimizer/libs/php/ to web-optimizer/cache/ .
3. .htaccess usage is allowed only for Apache websites. If your website is hosted via php as CGI, and .htaccess isn't supported, it's disabled (enabling .htaccess logic on an unsupported environment leads to a disaster for your website).