This slow appears either in the IDE / Standalone (with Xojo 2015r1) and with 2015r4.1 running in the IDE.
The news from earlier today is this does not appens with the same project, but another (different) window that does not use the Sub-Classed ListBox !
The Sub-Classed ListBox have EditCopy (a Menu Handler) and a Note. That is all.
No, the story continues.
When I deleted the Sub-Classed instance, it had bad effects on my ListBox. I reverted the project to the previously saved state and changed the ListBox Super to Listbox (with the Mouse).
Then, I deleted the Sub-Classed instance, and make a Run. Now, I get errors because I have duplicate Events (that does not exists in the Sub-Classed ListBox I just deleted !).
Where are my hairs and my hands to pull them ?
I reopen the window with the Sub-Classed ListBox and it appeared that its class is the now defunct cLB (the Sub-Classed ListBox), not the Listbox class I set it to minutes ago ! I am doomed !