As John mentioned, there should be a dialog during the installer that lists the detected Max installs to add Krakatoa to.
You can still manually add Krakatoa to the plugin.ini (or the localized one for 3ds Max 2013 ie. en-US\plugin.ini) but you need two entries:
Krakatoa=C:\Program Files\Thinkbox\Krakatoa MX\3dsMax2013
ThinkboxSchematicControl=C:\Program Files\Thinkbox\SchematicControl\3dsMax2013
While trying to debug this problem I found a bug in the installer that prevents the 2013 plugin from being added to plugin.ini unless Max 2012 is present. Whoops. That is why it wasn’t automatically adding the Max 2013 plugin.ini entry. As you discovered, you can work around this by manually adding the entry.
I’m not sure why the Max 2010 build would be acting up. I’ll look into that for you. You said it was reporting:
That could mean that tbb.dll is not in the 3ds Max root directory (I thought it was installed as part of Max, but I might be hallucinating). Can you tell me if you found it there?
That DLL is optional, and we had thought we were not using the features that required it but Paul found some code buried in Krakatoa that was causing that dependency. We’ve removed the offending bits from the next build which will remove the tbbmalloc.dll requirement.