My best guess would be that your domain has been used before? I also get lots of requests on my domains to files that are long gone (couple of years).
We registered both .SE and .COM in April, and I don't think either had been used before. The .COM is currently parked, I'm seeing all of this on the .SE site.
The referals I've seen appear indicate Spanish clients; There could be a mixup (Spain = .ES), but the domain name .ES isn't registered by anyone.
I don't think there's much to be too concerned about, I was merely curious what this might be.
This is why I'm confused about these requests :)