Most of the issues you describe sound like template issues. let me explain:
There are different templates for each part which can be used, such as the product list, the product page, the shopping cart. In order to use the new ecommerce version you should not use a template which was built for an older ecommerce version. Too much has changed in ecommerce recently. Many of themes which have their own templates for ecommerce had been built some time ago, so if they contain ecommerce templates, then they fit for the older ecommerce versions.
Now your oldenglish theme was released 03 Sep 08, and it says that it is compatible with ecommerce, thus I assume that it contains its own templates for ecommerce. If so, they can only be written for an ancient version of ecommerce. In this case replace the oldenglish_ecommerce templates with the generic templates from the ecommerce module. You might need to adapt them to fit your oldenglish theme, use the old oldenglish templates as samples.
If your oldenglish theme does not contain its own ecommerce templates then check what templates are used, and make sure they are the ones from your version of ecommerce.