PetScKrylovSolver sometimes crashes in parallel

When I run the unit test test/unit/la/python/KrylovSolver.py with three processes it crashes frequently with the following error message:

Warning -- row partitioning does not line up! Partitioning incomplete!
[2]PETSC ERROR: MatHYPRE_IJMatrixCreate() line 76 in src/dm/da/utils/mhyp.c
[2]PETSC ERROR: PCSetUp_HYPRE() line 112 in src/ksp/pc/impls/hypre/hypre.c
[2]PETSC ERROR: PCSetUp() line 795 in src/ksp/pc/interface/precon.c
[2]PETSC ERROR: KSPSetUp() line 237 in src/ksp/ksp/interface/itfunc.c
[2]PETSC ERROR: KSPSolve() line 353 in src/ksp/ksp/interface/itfunc.c
[2]PETSC ERROR: PCDestroy_HYPRE() line 204 in src/ksp/pc/impls/hypre/hypre.c
[2]PETSC ERROR: PCDestroy() line 83 in src/ksp/pc/interface/precon.c
[2]PETSC ERROR: KSPDestroy() line 695 in src/ksp/ksp/interface/itfunc.c

or with this message:

Inconsistent partitioning -- HYPRE_IJVectorCreate
[2]PETSC ERROR: VecHYPRE_IJVectorCreate() line 19 in src/vec/vec/impls/hypre/vhyp.c
[2]PETSC ERROR: PCSetUp_HYPRE() line 118 in src/ksp/pc/impls/hypre/hypre.c
[2]PETSC ERROR: PCSetUp() line 795 in src/ksp/pc/interface/precon.c
[2]PETSC ERROR: KSPSetUp() line 237 in src/ksp/ksp/interface/itfunc.c
[2]PETSC ERROR: KSPSolve() line 353 in src/ksp/ksp/interface/itfunc.c
[2]PETSC ERROR: PCDestroy_HYPRE() line 201 in src/ksp/pc/impls/hypre/hypre.c
[2]PETSC ERROR: PCDestroy() line 83 in src/ksp/pc/interface/precon.c
[2]PETSC ERROR: KSPDestroy() line 695 in src/ksp/ksp/interface/itfunc.c

Note that this happens only in about 10% of the runs, so there seems to be a race condition somewhere.

The following code (which is essentially a part of the unit test) reproduces the bug on my computer (Ubuntu 12.04 with PetSc installed through apt-get) when run with

mpirun -np 3 python KrylovSolver.py

from dolfin import *

# Assemble system
mesh = UnitSquare(32, 32)

V = FunctionSpace(mesh, 'CG', 1)
bc = DirichletBC(V, Constant(0.0), lambda x, on_boundary: on_boundary)
u = TrialFunction(V); v = TestFunction(V);
u1 = Function(V)

# Forms
a, L = inner(grad(u), grad(v))*dx, Constant(1.0)*v*dx
a_L = inner(grad(u1), grad(v))*dx

# Assemble linear algebra objects
A = assemble(a)
b = assemble(L)
bc.apply(A, b)

# Get solution vector
tmp = Function(V)
x = tmp.vector()

# Get solution vector
x_petsc = down_cast(x)

# With PETScPreconditioner interface
solver = PETScKrylovSolver("gmres", PETScPreconditioner("amg"))
solver.solve(A, x_petsc, down_cast(b))