Self referencing loop detected for property 'ManifestModule'

Hi,

We are getting the same error stacktrace described in this post:

http://world.episerver.com/forum/developer-forum/EPiServer-Search/Thread-Container/2014/8/Indexing-issues/

But we're getting it when attempting to do a nested search in Find. We have a nested convention applied:

SearchClient.Instance.Conventions.NestedConventions.ForType<Variant>().Add(v => v.ListingDates);

Where listing dates is a collection of a custom object type.

And in the search query:

            DateTime now = DateTime.Now;
            var exp = new NestedFilterExpression<Variant.Models.Variant, ProductListingDateRange>(
                item => item.ListingDates, 
                item => item.ListedFrom.Exists() & item.ListedFrom.LessThan(now) & item.ListedTo.Exists() & item.ListedTo.LessThan(now), 
                SearchClient.Instance.Conventions);
            return new FilterExpression<IContent>(x =>
                x.MatchType(typeof(Variant.Models.Variant)) &
                ((Variant.Models.Variant)x).ListingDates.MatchItem(item => exp));

It blows up with the error text 'Self referencing loop detected for property 'ManifestModule' - the JSON.NET serializer seems to be choking on a recursive reference within the Assembly, though why it's trying to serialize the assembly I have no idea!

Any pointers appreciated as to whether this is a bug or a problem with the way we're using Find.