I'm trying to install Prism 3cx (or the updater) on a Mac with OSX. The installer stops, saying that it requires 4096K of physical memory, but my computer has several GB of memory.

The installer doesn't work on computers with lots of RAM, and gives an silly error message about too little RAM. Please use this alternative installer instead:
http://graphpad.com/downloads/p3cxfixed.sit.bin

The password to extract the file is 2gbram