As you have noticed, by default OpenAccess creates bidirectional associations - you have a reference on one side and a collection on the other side. This indeed could lead to serialization problems.
The easiest way to verify if this is the problem is to disable one of the navigational properties and leave either only the reference or the opposite collection - just decide which one is more useful to you. This can be done by double-clicking the association in the designer and unchecking the checkbox for one of the navigational members. You could take a look at this article
for reference how to use the editor.
Hope that helps.
OpenAccess ORM Q2 2013 brings you a more powerful code generation and a unique Bulk Operations support with LINQ syntax. Check out the list of new functionality and improvements shipped with this release.