Intermittent Problem Persisting HABTM relationships

We are having an intermittent problem with has_and_belongs_to_many
where the join table record is not created. For example, we have a
HABT relationship mapped on both sides of models InFile and Sponsor.
Our code looks like this:

sponsor = Sponsor.find(sponsor_id)
in_file = InFile.new(attributes)
in_file.sponsors << sponsor
in_file.save

Occasionally the new join record in in_files_sponsors is not
inserted. It takes a while for this to start happening, but once it
starts happening it continues. We are using Rails 2.02 with Ruby
1.8.5.

Thanks!

Steve and Jonathan

Try something like this:

Sponsor.find(sponsor_id).in_files << InFile.create(attributes)

I'm wondering if trying to make the association before the in_file
object has been saved is causing the problem. But I can't explain why
that would only cause an intermittent problem.

Aaron