I have precisely the same problem. I can retain even the most absurd memories about someone, but when asked to produce a given name, I often draw a blank. It could just be me, but when I think about someone, I think entirely in images and abstracts. The name seems so trivial and disconnected from who they really are, that I cannot produce it without work.
On an odd aside, having many friends who are furries has given me an odd perspective on this! Most furries pick their own "patron" species in a way that's sympathetic to their own personalities. This can be deliberate, but or more often, I think, it is intuitive. I myself am a Rabbit, because I feel a kinship on an intuitive level, but ultimately because I process stimuli as I imagine a rabbit does. (Think "Animals in Translation".) This connection between species and personality is far from an exact science, but it is far more telling than a given name.
It may take me a few moments for me to remember the given name of a close friend I've had for many years - it's just an arbitary symbol that bears no resemblance to the person. Even after hearing a given name, it may still take me a moment to connect it to an actual person. But the connection between the individual and his patron species is always immediate. When someone mentions a friend by patron species: dragon, jackalope, lion, fox, cat, winged rabbit, polar bear, owl, yoshi, chipmunk... the connection is immediate.
I don't expect a non-fur to share this experience, but I do wonder why this would be.
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Sainte atha ma u Hrair, kan zyhlante hray u vahra ma hyaones.
My heart has joined the Thousand, for my friend stopped running today.