bSortable problem

hi,
if i set bSortable: false in first column , all others columns not sortable.
if i set bsortable any other column words fine.

in first column mouse click is disabled, in others click is enable but not work.

All:
"aoColumns": [
{"bSortable": false},
null,
null,
null,
null,
null,
],


in firebug log is the same response
FIRST DISABLE PROBLEM
bSearchable_0 true
bSearchable_1 true
bSearchable_2 true
bSearchable_3 true
bSearchable_4 true
bSearchable_5 true
bSortable_0 false
bSortable_1 true
bSortable_2 true
bSortable_3 true
bSortable_4 true
bSortable_5 true
iColumns 6
iDisplayLength 10
iDisplayStart 0
iSortCol_0 1
iSortingCols 1
sColumns
sEcho 6
sSearch

SECOND or + FINE
bSearchable_0 true
bSearchable_1 true
bSearchable_2 true
bSearchable_3 true
bSearchable_4 true
bSearchable_5 true
bSortable_0 true
bSortable_1 false
bSortable_2 true
bSortable_3 true
bSortable_4 true
bSortable_5 true
iColumns 6
iDisplayLength 10
iDisplayStart 0
iSortCol_0 0
iSortingCols 1
sColumns
sEcho 2
sSearch



i am wrong?

thans

Davis