This came up with another customer recently. The command leSetObjectSelectable("ruler" nil ) only works once the layer palette has been initialised (i.e. a layout is being displayed), and so it does not work in your .cdsinit.
I developed the following workaround which should help you:
This would be global for a session, so you might choose to
activate this on/off with bindkeys (the filter can be removed by:
leUnregUserObjectSelectionFilter() - there is no function to
see if a filter is set or what the filter is, as far as I can tell).
I filed CCR 1107225 for this problem, I suggest that you file a case with Customer Support and reference this CCR, requesting that it is fixed for you also - more requests allow R&D to know it is important for more than one customer, and they can prioritize accordingly.
I hope this helps you!