How to display Custom Fields in multiple languages;
When you first install Contact Enhanced, all Form Fields are set to ALL languages. So first, you need to copy the current Form Fields to one of the languages.
Go to Components -> Contact Enhanced -> Form fields, Select ALL Fields you need in multiple Languages, then click on the Batch button and move the fields to the new language.
One by one:
Go to Components -> Contact Enhanced -> Form fields, open the original form field set the language to English (or another language) under the Publishing Info slider and then change the name of the field for the new language and set the language to the chosen one and hit Save as a Copy and you are done.
In Joomla 1.5 it is a bit more complicated because it requires you to use Joom!Fish and it cannot translate multiple database tables per component. Please read this forum post.