problem with IBRION=1

[TAT]

Hi,
I am trying to calculate Phonon DOS for Carbon-La system. I am using PAW+LDA potentials. when I try to use IBRION = 1, the run crashes after 1 ionic step and gives me following error. IBRION = 1 runs fine with other systems that I tried.

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One of the processes started by mpirun has exited with a nonzero exit code. This typically indicates that the process finished in error.
If your process did not finish in error, be sure to include a "return
0" or "exit(0)" in your C code before exiting the application.

PID 28990 failed on node n0 (127.0.0.1) due to signal 11.
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my Input file looks as follows
ADDGRID = .TRUE
PREC = High
ENCUT = 300 ! Energy cutoff
ISTART = 0 ! Start from scrach
ICHARG = 2 ! Take superposition of atomic charge density
EDIFF = 1E-8
EDIFFG = -.0001 ! Break condition for ionic relaxation in term of
NSW = 1000 ! number of Ionic steps
IBRION = 1 ! Conjugate gradient algorithm
POTIM = .01 ! scaling constant
ISIF = 2 ! Relax ions only
ISYM = 2
SYMPREC = 1E-8
ISMEAR = 0 ! Gaussian Smearing
SIGMA = .03 ! Width of smearing
NPAR = 1
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and when ever I try to use IBRION=2, the structure doesn't converge and gives me following error after may be 40 to 50 SCF
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ZBRENT: fatal internal in brackting
system-shutdown; contact gK immediately
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Please provide some suggestions as to what is wrong.
I am sampling with 6x6x3 mesh

[fanghz]

It seems that the EDIFFG is too small. I think the system is hard to convergence under such extremely small force condition.