Dear all,

when I try so specifiy my 2nd level model for a flexible fac I receive this error message:

Failed 'Model estimation'
Index exceeds the number of array elements (0).
In file "/home/me/spm12/spm_reml.m" (v7178), function "spm_reml" at line 62.
In file "/home/me/spm12/spm_reml.m" (v7178), function "spm_reml" at line 213.
In file "/home/me/spm12/spm_est_non_sphericity.m" (v7577), function "spm_est_non_sphericity" at line 281.
In file "/home/me/spm12/spm_spm.m" (v7738), function "spm_spm" at line 433.
In file "/home/me/spm12/config/spm_run_fmri_est.m" (v7354), function "spm_run_fmri_est" at line 36.

Ive read that I might be using wrong paths but I have checked cerefully and it is not the case.
Does anyone have experienced this kind of error message before or have an idea what I should further check?

Thank you so much 
cheers