I rarely talk about short lived timely issues such as this one but it was a bit too pervasive to pass up and the facility here has just been bitten by it.
I’m talking about spontaneously disconnecting shaders.
Background info (read these):
The following script partly automates the solution described by eX-SI Support so if you have many libs it almost eliminates human error. It seems to have worked for us so far as a preemptive measure before scenes break or after having spent too much time fixing a scene. Import an asset, material preset or fix a broken scene, go through the hoops. This is not fun but until there is an official fix, we’re kinda stuck.
Application.MatLibFixStep1() which will convert material libraries to external references, prompt you to save the scene and quit Softimage.
Restart Softimage, open the scene you saved previously and run
Application.MatLibFixStep2() which will reconvert the material libraries to internal storage.
Jean-Sebastien’s workaround is also worth investigating if the above doesn’t work for you (see the Softimage mailing list thread linked above).