libnss version 2:3.32-1 on i386 is built with SSE2 on, which prevents
it from running on pre-SSE2 systems. On my Pentium III system, this
results in Firefox crashing at startup inside libfreeblpriv3.so with
SIGLL on a movq from memory to xmm0. Note that, although upstream
Firefox requires SSE2, the Debian package does not — in fact, Firefox
as provided by Debian running fine on Pentium III is the very reason I
installed Debian on this machine.
While an SSE2 build has obvious performance advantages, I still
believe it's a bug, because those who care about performance have
modern machines and use amd64, while i386 is mostly used on legacy
As a temporary workaround, downgrading to libnss 2:3.31-1, which after
cursory look contains no SSE2 code, makes Firefox run fine.