Change 0 to .F. and 1 to .T.

or replace the code with

thisform.grid1.column5.check1.value = !thisform.grid1.column5.check1.value

Why do you call the click event of the checkbox? Are you try to refresh the value? In that case
THISFORM.GRID1.COLUMN5.REFRESH

>if thisform.grid1.column5.check1.value = 0 && get error 107 here
> thisform.grid1.column5.check1.value = 1
>else
> thisform.grid1.column5.check1.value = 0
>endif
>
>thisform.grid1.column5.check1.click()