Eircom connectivity issue


I've ran into a puzzling scenario and I thought I'd ask around to see if anyone else has an idea.

I have a customer who operates a server on our network who informed me that a customer of his out of Ireland is having connectivity issues to it. The ISP in question is Eircom, and the block that seems unreachable is

Any trace to an IP in that block drops off the Earth at the edge of the Tier 1 provider that we connect with, such as AT&T and Sprint. I've also tried Level3, but the traffic goes over to AT&T in the end anyhow. I've checked Level3 and Sprint's looking glass and performs a traceroute from there, and I get the same result, so it doesn't appear to be an issue with our network.

I'm at a loss and my customer told me that his customer has already contacted Eircom and they are at a loss to explain the disconnect as well. Does anyone have some insight into this?