With an open plan file:

1: Select an object (not the first one :)

2: Use shift cursor-up to select the target above

3: CPU hits 95%+ for 10secs or so

4: It looks like a blank (default?) object is inserted into the plan (see attachment)

A possible, very odd, side-effect appears to be that after the above is complete I cannot enter text into any AP fields (including the Bug Report form!).

Attachment: MultiSelect.jpg