Running program freezes after a while

Hi,

I compiled my program with ifort (with ifort  -parallel -O3). The program runs for a while, but the computations finally stop and the program is in the state "S" (interruptible sleep) according to ps. Here is the list of a minimal code that causes a problem:

      program bkmit
      implicit double precision (a-h,o-z)
      parameter(nr=1000,dt=5d1,nt=400000000,no=100,o1=1d-9,o2=1d-7)
      real*8 p(3,nr)

      do io=1,no
      o=o1
      do ir=1,nr
       p(1,ir)=0d0
       p(2,ir)=0d0
      enddo
      do it=1,nt
       do ir=2,nr-1
        p(3,ir)=p(1,ir)+1d7*(p(2,ir+1)-p(2,ir-1))
       enddo
       p(3,1)=-p(3,2)
       p(3,nr)=p(3,nr-1)
      enddo
      write(*,*) o
      enddo
      end

Note that for nr=100 the code works fine. Any idea what causes the problem? Thank you very much.

With best wishes

Jiri