VERY BAD NEWS! internal error in subroutine PRICEL VASP4.6

[Piekarz]

I did calculations for the supercell 1x1x1 40 atoms and space group P2/1c.
After increasing the cell to 1x1x2 the calculations stopped with the output:

VERY BAD NEWS! internal error in subroutine PRICEL (probably precision problem, try to change SYMPREC in INCAR ?):
Sorry, number of cells and number of vectors did not agree. 2

I checked that POSCAR is OK, and program FINDSYM found correct symmetry.
I changed the SYMPREC parameter to 1E-3 without any improvement.
After changing SYMPREC to 1E-2 calculations started, however, VASP did not recognized
the space group.