So, I found that dreaded bug I was chasing for several days. It was, uh, in endianness-conversion macros I ripped out of glib, and apparently did that wrong. I feel so stupid now it’s not even funny… :\
PS. Word of advice for you, lads: recalling “best of Sluggy.com” when razor-shaving is, umm, not the best idea one can get. Really ;)