acorn may have been referring to windows virtual memory

the only xara program setting I know are on the tiune-up tab of options but I can't remember the last time I tried changing any of these so I can't offer advice on them

in a graphics only file you might try opening a new blank document and copy/paste objects one by one and see if you can find one causing issues - since you have a similar file that is ok it may well be an object that is say, too complex, or that is grouped with something way off the screen making a very large object - switching to wireframe and zooming out may also identify anything invisible that should not be there