This week I upgraded some work projects to Quartus v12 SP2 and I ran into an interesting bug, which has an obscure patch to fix it. I thought I should share.

The problems happens when you update a symbol/block in a schematic (bdf) file, after which anytime you try to compile you get a nasty error that crashes Quartus.

The error code is basically this:
Internal Error: Sub-system: DBMUI, File: /quartus/db/dbmui/dbmui_manager.cpp, Line: 1179

At this point I found you need to apply this Patch 2.16 to fix the problem.

When I ran the patch installer, it was unable to locate my Quartus installation. I first tried to use the quartus subfolder, but eventually found I needed to patch to this directory:
C:\altera\12.0sp2

Hopefully that helps solve your problem.