Sorry, this is not a known issue.
There are many things that could be causing it. First I would look at your Site definition to make sure the settings are correct.
Look at the Local info tab, make sure the site URL is valid. Have you selected the option to Create Links relative to the Site, or Document? It should be set to Document.
Next check the Testing server settings. Is the URL Prefix valid?
4.5.0 is not the most recent version, you may want to uninstall that version from the extesnion manager and install version 4.5.2 which is available for download on the eCart download page in the download center.