Hi Mohan
you need to calculate cost estimation and with out save and no update in material master.
I think you need not change any thing in costing variant update tab.
and you can use both CK11N and CK40N to calculate cost estimation.
CK11N can be run to check Induvidual cost estimation, then you ignore Mark and release
CK40N you run this transaction upto Analysis and do not run Mark and Release.
mostly the error is due to changes you made in the system.
please reset costing variant and try.
regards
Vasu