It appears that adding a second instance of Aalto to a session while the UI of the first instance is open will consistently crash the plugin host.
All of the following combinations exhibit the problem:
OS: Mac OS X 10.6.7 or 10.8.2
Host: Live 8.3.4, Logic Pro 8.0.2, Numerology Pro 3.1.1
Aalto: 1.3.1 32-bit AU or VST
Repro steps in Live:
(1) Drag Aalto from the browser to "Drop Files and Devices Here"
** leave the plugin UI window open, if it isn't open, open it.
(2) Repeat (1) => Live crashes.
Thanks for the good report.
Fixed for 1.3.2, coming soon.