Yes, I know I should upgrade to Aperture 3, but as Aperture 3 seems to have the same problem for many working with raw images....?
Keep in mind, that happy users are usually not posting here - Aperture 3.5.1 is working well for many of us with Mavericks, and Aperture 3 it is the only supported version for the newer MacOS X versions since Mavericks. Some Aperture 2 features simply do not work any longer, like the Loupe, but it should not crash. Nevertheless, I strongly recommend to upgrade to Aperture 3. Only, before upgrading, you should get Aperture2 to work again, so you can repair and rebuild all your Aperture libraries in Aperture 2 before upgrading. That is recommended by Apple, and will make the upgrade easier, see:
A note on upgrading your Aperture library (scroll down to the bottom of the ducoment)
also.
Aperture 3: Tips on upgrading an Aperture 2 library to Aperture 3
I am panicking a bit, as I have more than 12,000 images from a travel through half the world, that I use every day and now cannot access any?
First thing to do - check your backups, if they are current and working. If not, make an additional backup. I would not overwrite your previous backups right now.
How full is your system drive and the drive with your Aperture library? Do you have enough free disk space as working space for the system? Keep at least 20GB free; if the disk space becomes critically low, that may cause crashes.
What changed, directly before the crashes started? That might give us a clue. Did you install new software? Update software? Import new photos or videos? Did you move your library? Ran any cleaning/maintainance applications? Check all software on your system (preference panes/ device drivers, plug-ins (not only photo plug-ins, also video codecs, audio plug-ins), fonts, if they are compatible with Mavericks.
I dont have Aperture 2, so I cannot test it on Mavericks.
Your last import may have imported corrupted image files or videos, that cannot be processed and need to be removed. Or a crash may have corrupted the internal database files.
If you have ensured, that the library is backed up and you have only Mavericks compatible software installed, try, if repairing or rebuilding your library will help; see:
Aperture 2: Troubleshooting Basics
-- Léonie