Divergence in 8 node parallel solution
 

I am running fluent 6.3 from a journal file. when run it parallel on a 4 node computer i get the solutions but on a 8 node computer it gives divergence detected on AMG solver: temperature error. i could not find the reason for it. Can some one help me??
p.s. i run this journal for different angle of attacks from -4 to 20 degrees for a symmetric aircraft geometry and this happens only for 0 and 4 degrees in pressure based realizable k-e model.