[Petrah]

Have you ran the repair tool located in the root directory of the game? If yes, and it found no errors then another option, which is rather tedious but it's all part of troubleshooting, is to start from scratch again (delete the Cache, Interface, and WTF folders) and install one of your addons. Run the game for a day or so and see if it crashes. If it doesn't, install one more addon. Rinse and repeat until you figure out which addon is the culprit.

I've seen some of those out of memory errors on the tech support forum from an addon on systems with more than 4 GB of ram. At this point I think it would be better to troubleshoot the addons themselves rather than rushing out to buy more ram when you might not have to.