When selecting multiple objects in Archicad to reference into grasshopper  (ie in GH, the "Select Multiple ..." option), you can only manually select objects in Archicad one by one.  cmd/ctrl-A doesnt work.  nor does the selection rectangle, or pre-selecting objects before starting the command.
 
this might be fine if you only wanted to import a very small number of objects, but makes the live connection problematic if there are a lot (in my case, hundreds) of objects, often buried inside/behind each other.
 
---UPDATE---
this problem only occurs (as far as I can tell) when you are in a teamwork project, and you do not have the objects already reserved.  I guess the connection is probably trying to write info about the link back to the objects and failing.  however this doesnt explain why selecting one by one works...
 
Ben
 
Rhino 7 (7.23), GH (1.0.0007), AC 25 (AUS 5010 full), Live Connection (3003)