Baculovirus expression heterogeneity

[BIOTEC54]

Over the past several years, my lab has produced many differing types of
proteins in insect cells using the baculovirus system. During plaque
purificiation, we always pick several (5-10) recombinants (+ for insert
via PCR) for expression analysis...and nearly always see a high degree of
expression level heterogeneity between the clones ranging from little to
no r-protein production to high level production.  Since we have no time 
to characterize every clone...we simply move on with the highest
expressing clone....but always wonder "what happened" ?
Is this a general feature of the system that other labs experience? ...and
has anyone a (good) explanation/data/reference/ etc?  Thanks

Hank George
DuPont Merck Pharmaceuticals
EXPRESS YOURSELF!