Sorting GFP-labeled fibroblasts to culture

Dear Flowers,  I have a client who is trying to sort GFP-labeled
fibroblasts to grow in culture.  The cells are sorted in PBS into
culture medium, using a FACSCaliber.  After spinning down, GFP- labeled
cells were observed under the fluorescent microscope.  They were plated
and looked at the next day under the fluorescent microscope again.  The
cells that had attached were not fluorescent.  Any ideas about what is
happening; are the labeled cells not viable or not producing GFP now? 
Thanks for any help you can offer.  Jane Miller, Dept. Micro. Mole.
Path., TX A&M Hlth. Sci. Ctr., College Station, TX  77843