afni.nimh.nih.gov

... and to note for future generations:

From further investigation offline, it seems like this error was caused by a server issue. Various subjects were submitted on an HPC system, and probably on just a small number of servers some subjects' processing failed for some reason. But upon re-running the APQC HTML generation, things worked for those subjects (presumably they ended up on a different operating system or that system had been fixed in the meantime).

--pt