Handling tattlers?

Hi, folks --

I'm sure there's a 'cast for this somewhere, but none of the keywords I've used lead me there. I'm a mid-level manager in our group, and I often have to work with folks in different groups in our organization. A peer in one of these groups seems to have picked up a really bad habit recently; every time I've emailed him or replied to an email with bad news (subjectively; in at least some cases, I had no idea I was delivering news that would be ill-received), instead of getting a reply, his director would escalate immediately to my director to request a change in what we're delivering to them.

I use the term "tattler" above, but I'm not so sure that's accurate. Our group's doing nothing wrong, and this is hardly the type of stuff described in, say, the "dropping a dime" podcast. But it strikes me as incredibly unprofessional and passive-aggressive. I'd completely get it if he were finding me a roadblock and if I refused to negotiate with him, but this is his first reaction, and it really does remind me of the old elementary school tattling. Since we're both in different parts of the organization that come together rarely, we don't have a regular working relationship, so I can't tell if this is typical behavior for him.

One additional thing that may or may not be a factor; his director is new (just hired about three months ago), strong-willed, and been charged with making some big changes. It's possible that this is top-driven, but I just don't know.

Thoughts on the best approach to take (or links to good posts or episodes that cover this)?

Thanks!