As stated, the updatemanager requested that I update my hardware support. I believe it said that my hardware stack as it existed previously wouldn't be supported after 8/07. I installed the update, rebooted, get to the login screen, everything seems fine... login successfully but nothing loads; after about 10 seconds of blank desktop background, VMWare Tools kicks in, makes the screen the correct size, and suddenly the screen goes black.
Rebooting doesn't help. Setting 3d acceleration to "off" in the VM settings helps, and lets me do things like run a terminal just fine (so I believe this problem should be solvable from within Ubuntu.... I'd like to avoid wasting my time making another VM and migrating the filesystem, preferably maintaining the most up-to-date 12.04 possible); this information may be useful in diagnosing the issue but is not a long-term solution, as it makes many graphical features of Ubuntu anywhere from buggy to nonexistent.
My graphics card is the AMD (ATI) FirePro M5950 (since this seems to be a graphics-related issue, possibly with a new driver that came with the update? But for the record, I have already tried adding
mks.gl.allowBlacklistedDrivers = "TRUE" to the relevant vmx file, to no effect whatsoever).