Some users have reported crashes when they open the render tree or Material Manager. For some users, this happens after a period of extended usage; for others, it appears to be scene- or geometry-specific.
I’ve had users send me scenes with geometry that appeared to crash the render tree and Material Manager, but when I tried on my machine, everything worked fine. So, it’s a bit of a mystery.
There is a workaround however: open the render tree and Material Manager before you load your scene. After that, you can work normally.
You could use an OnStartup event to automatically open those views when Softimage starts. I believe you could just open and close them at startup, and then everything will be ok afterwards.
eX-SI 
I have the same problem while using preferences from remote computer. But when I use my local preferences all works fine
Getting the same error, when loading several tabs in the material manager with render tree visible, XSI crashes every so often. This only happens with multiple material tabs, never had this problem before tho – now it persistently keeps me from working on my assignments.