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[Fwd) ccp4 problem stuff

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Dear all,

I am experiencing some problems with the refinement (fiting) step of 
AMORE. My crystal appears to be P21 (a=71.23 b=57.26 c= 116.79, 
alpha= 90 beta = 103.27 gamma= 90) with b-axis unique. The data were 
integrated and processed in mosflm and scaled in scala (R < 5%). 0k0 
reflections clearly indicate a 2-fold screw axis. AMORE appears to 
work fine giving translation search results of

alpha = -0.05  beta = 88.66  gamma = 345.08
Tx = 0.2019 Ty = 0.000 Tz = 0.4464
Cc = 24.3 Rfac = 56.3

Upon refinement (the fiting step) the value for a fractional
translation in Ty increases enormously often giving a line of
asterisks e.g. (for above example) 

alpha = -1.46 beta = 87.93 gamma = 344.55
Tx = 0.2038 Ty = ***** Tz = 0.4493
Cc = 43.3 Rfac = 54.0

This crystal is of a protein which can also grow in a tetragonal form 
where the c axis is large (over 250 Angstroms)

Could anyone offer any advice on where possible reasons for this come 
from and how best to tackle them, thanks
University of Birmingham, U.K.