[pdftex] Problem with underscores in URLs

[Robin Fairbairns]

> ! Undefined control sequence.
> <argument> ...ct \global \let \OT1\textunderscore 
>                                                   \unhbox \voidb at x \kern
> .06...
> l.7 \htmladdnormallinkfoot{token processor}{\_}

this has all the hallmarks of fragile command in moving argument.
however, it doesn't happen for me with your test program.

try posting a test program that corresponds to the log you posted --
i.e., do the obvious thing and post a minimal failing document.

we _don't_ want to see your entire original document, just the
smallest number of packages that provoke the problem, and the
\listfiles output so we can see the version numbers.