What I think works is being totally forthcoming about problems, risks, etc. in the past and present, but maybe being a bit optimistic about future possibilities. i.e. "This quarter our sales were down 10%, but we think it was due to reason x, and we have strategy y in place to address that. We will be monitoring closely and adjust as needed.".

You don't want to say "there wasn't a problem", but you also don't want to say "sales went down, we have no idea why, we're just going to continue" or "sales went down, we're doomed."