Calu-3 cell line do not grow properly - (Mar/01/2012 )

I have a problem... A collaborative lab send me the cells by mail as had send some other cell lines. But this Calu-3 appears to have a slow growth. The flask is in the incubator for more then 2 weeks and there is only less then 50% confluence. The cells divide but most of it remain detached in the medium and are removed during the medium replacement...
The medium used is the same that in the other lab. DMEM:F12 with 10% FBS, 1%L-glutamin, 1% NEAA and 100 mg:
ml penicillin/streptomycin. How long did normally Calu-3 cell line to get confluent?
Can anybody help me? Please...

Any pretreatment of the flasks? You might want to coat the flasks before culturing your cells. Ar you using non adhesive flasks?