Okay, I'm wondering if there was a "variant edition" of an Ultimate Spidey issue I never heard about.
From the letters page of issue #101:
Q: "Who is Arachnoman and what issue is he in?"
A: "Arachnoman appeared in a special out-of-continuity variant edition of issue 54, where, instead of making a Spider-Man movie, the filmmakers were making Arachnoman. Long story. Ended happily."