[ccp4bb] reproducibility of protein crystals

[anita p]

Dear Crystallographers,
 I have got my protein crystallized once and then it is not reproducing,
though I am using the same batch of protein and same condition.
 What are the reasons behind nonreproducibility of protein crystals?
 I am very new to this field hence I apologize if it is a lame question.
With regards
Anita