Package: pari
Version: latest git

Here is a transcript from a session.  Increasing the realprecision does not seem to help:

Myprompt: ~/src/pari-git/gp -f 
          GP/PARI CALCULATOR Version 2.6.2 (development 15614-ed95d4f)
          amd64 running linux (x86-64/GMP-5.0.2 kernel) 64-bit version
    compiled: Dec  3 2013, gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) 
                 (readline v6.2 enabled, extended help enabled)

                     Copyright (C) 2000-2013 The PARI Group

PARI/GP is free software, covered by the GNU General Public License, and comes 
WITHOUT ANY WARRANTY WHATSOEVER.

Type ? for help, \q to quit.
Type ?12 for how to get moral (and possibly technical) support.

parisize = 8000000, primelimit = 500000
? allocatemem()
  ***   Warning: new stack size = 16000000 (15.259 Mbytes).
? allocatemem()
  ***   Warning: new stack size = 32000000 (30.518 Mbytes).
? allocatemem()
  ***   Warning: new stack size = 64000000 (61.035 Mbytes).
? allocatemem()
  ***   Warning: new stack size = 128000000 (122.070 Mbytes).
? allocatemem()
  ***   Warning: new stack size = 256000000 (244.141 Mbytes).
? default(realprecision,250)
? x^11 - 317064055*x - 2017680350
%2 = x^11 - 317064055*x - 2017680350
? bnf=bnfinit(%,1);
? bnfnarrow(bnf)
  ***   at top-level: bnfnarrow(bnf)
  ***                 ^--------------
  *** bnfnarrow: precision too low in floorr (precision loss in truncation).
  ***   Break loop: type 'break' to go back to GP prompt
break> 

? default(realprecision,100000)
? bnf=bnfinit(bnf,1);
? bnfnarrow(bnf)
  ***   at top-level: bnfnarrow(bnf)
  ***                 ^--------------
  *** bnfnarrow: precision too low in floorr (precision loss in truncation).
  ***   Break loop: type 'break' to go back to GP prompt