Latest iceweasel 31.2.0esr crashes X on wheezy 7.7

[David <bouncingcats@gmail.com>]

I run wheezy 7.7 on several 12" IBM X24 machines with 640k RAM.

I recently upgraded
iceweasel:i386 24.8.1esr-1~deb7u1 -> 31.2.0esr-2~deb7u1.

Before, it was fine. But now it crashes X frequently, so I lose my
work and have to restart X and all X apps. It happens intolerably
often.

I use adblock, downloadhelper, noscript, nukeanything extensions.

X is started by lightdm and lxde.

How can I revert iceweasel to the previous version?

Any other advice to investigate and restore previous stability and
functionality on this hardware?

Below are the relevant tail lines of ~/.xsession-errors

XIO:  fatal IO error 11 (Resource temporarily unavailable) on X server ":0"
      after 31 requests (31 known processed) with 0 events remaining.
parcellite: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
lxterminal: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
SciTE: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
lxpanel: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
pcmanfm: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
xchat: Fatal IO error 104 (Connection reset by peer) on X server :0.
XIO:  fatal IO error 11 (Resource temporarily unavailable) on X server ":0"
      after 2017 requests (2017 known processed) with 0 events remaining.
lxpolkit: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.

(devilspie2:4485): Gdk-WARNING **: devilspie2: Fatal IO error 11
(Resource temporarily unavailable) on X server :0.

XIO:  fatal IO error 11 (Resource temporarily unavailable) on X server ":0"
      after 156823 requests (156823 known processed) with 0 events remaining.
g_dbus_connection_real_closed: Remote peer vanished with error:
Underlying GIOStream returned 0 bytes on an async read
(g-io-error-quark, 0). Exiting.
iceweasel: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.