Also keep in mind, with a 32 bit application, it does not matter how much ram you put in a computer, a 32 bit application cannot address more than 4GB of memory. Windows can and can even swap other stuff up to higher memory addresses to free up more for the 32 bit app that is running.
One thing I have found that can help with really complex vectors in Flexi, if I am just moving some things around to group them for print, is to turn off show fills so it does not have to render/rerender all of the complex shadows, transparency, etc. Cannot see what it what since it is all just outlines but things move very quick then. I've determined the issue to more specifically be with transparency effects and how Flexi tries to render them while moving things around on screen. Can also the "design editor" window and simply turn those particular layers visibility off while moving things but you have to make sure to turn them back on.
Another bug I've found is with Illustrator files with multiple artboards. We often use artboards to chop things up for certain jobs. When opening in Flexi do NOT tell it to open all artboards at once. It will do it but random parts will be missing shadows or other effects with transparency. Open the first artboard, then import the same file again and import the next artboard, repeat, repeat, etc which can be tedious if the file has dozens of artboards.