[FLASH-USERS] v cycle not converging

[M.A. Latife]

Hi,
Dear All.
First of all sorry for disturbing you again. i am not good in using 
flash .  i am asking  many questions hope you will not mind.
i am simulating structure formation using FLASH 2.5 starting from 
redshift 25(Hydro+gravity+cosmology).
when i put uniform density over whole domain. i get warning v-cycle not 
converging and results become worse. i am using periodic boundary 
conditions  both for hydro+ gravity.
when i put over density at center (like Gaussian or Mexican hat) minimum 
density becomes small than it should be at particular redshift( like it 
becomes 1.0E-30 at redshift 15) although density should remain constant.
My 2nd question is when is when using cosmology should i use comoving 
coordinates when initializing conditions in initial block. if yes then 
how?. i am taking  block centres and dividing them by scale factor in 
Initial block .
any suggestions in this regard will be highly appreciated.
Kind regards
Latif