Maybe it's my outdated signature that threw you off, Chris. I _am_ using AC11. It's with AC10 migrated project files that I'm experiencing the difficulty.
EDIT: I just did a New & Reset All and the problem is the same: I built two identical walls with a clear fill, then changed one to a composite structure fill. If I copy the clear fill wall, it takes a fraction of a second. For the other wall, I counted just over 2 sec. Obviously there is something the matter with the programming here. Graphisoft? Comment?
Alex Zachopoulos
MacBook Pro 17" 2.4GHz, MacOS X 10.5.6, ArchiCAD 11 & 12, WinXP, Vista (well, not really Vista...)