This is a follow up to the bug labelled 5245 ( http://forum.ableton.com/viewtopic.php?f=26&t=110844 ).
Under the same conditions that previously caused the crash (ie renaming a previously unlabelled macro knob of a nested rack), the cursor doesn't appear until text is entered.
This is a minor annoyance, as it just means that there's no visual feedback that the knob is about to be renamed, but has no other side effect.
Live 8b26. Mac OS X 10.5.6