Iceweasel 38.2 seems broken

[Haines Brown <haines@histomat.net>]

After a Wheezy upgrade to iceweasel 38.2.1esr-1~deb7ui, iceweasel does
not display when started. An iceweasel process starts, but X server does
not pick it up.  

The terminal gives me: 

  console.error: 
    [CustomizableUI]
    Custom widget with id loop-button does not return a valid node
  
  and many lines like:

  2015-09-10 16:13:04: basic_code_modules.cc:88: INFO: No module at 0x0
  2015-09-10 16:13:04: basic_code_modules.cc:88: INFO: No module at 0xbf9ba83c

I find that "Bug 1097597 - Disabling loop breaks the world" reported 
last year for version 35 & 36 was supposedly fixed. But I also see Bug
798238 that version 38.2 crashes when certain pages (YouTube) are 
loaded. After the update Iceweadel worked a couple of days until I
visited YouTube, but this may only be a coincidence. I now can't get
Iceweasel to be seen by the X server at all.

I don't see any choice of versions in the debian repository and so can't
revert to an earlier version. Advice needed.