Does the ability to connect to a given IP address depend on the set of ultrapeers I'm connected to?

Here's the setting: I have two Limewire processes running on the same machine, each with a different set of ultrapeers. One of these processes has a connection to some host A (I can browse and download from A), but when I try to browse the same host A from the other Limewire process I sometimes am not able to connect.

I can imagine two possible explanations for this: (1) the ability to connect directly to a host depends on the ultrapeers I'm connected to; or (2) a host may have a limit on how many connections it admits. The first seems counter-intuitive, since, absent network partitioning, given an IP address of a computer that's alive, it should be possible to find a route to it regardless of which ultrapeers I'm connected to. But before I settle on the second explanation, I'd like to make sure that the first is ruled out.