>Yes indeed, even the smallest change triggers the error ...
>A lot of the controls on the form are base on classes. Could it be that there's a problem with one of these classes ? However, these classes are alos used on numerous other forms wihtout problems ...

I don't remember,
but it could depend on the names assigned to the members.

try this.
save the form as another scx: "crazyform.scx"

 modify crazyform.scx
 change it somewhere
 beginloop
    save
    if no error
      loopexit
    endif
    remove a member
  endloop