Excel Spreadsheet comes up not responding. what causes this?

Sometimes spreadsheets, like all other programs, simply freeze for no apparent reason. We close the application and when it is restarted (perhaps after a system reboot, the application functions perfectly and we are none the wiser for why this has happened.

Sometimes doing some function places a lot of strain on the computer and causes it to freeze, or causes it to appear to freeze when it just needs more time.

You need to determine if this problem is repeatedly associated with a particular function, and if so how to get around it. It is possible that the updating of linkages is highly memory intensive and causes the computer to not respond. If so, then you may need a computer with more grunt, or you may need to revisit what it is that you're asking Excel to do.

Perhaps in another copy of the file you can eliminate a proportion of the linkages to see whether this stops the computer from freezing. Try and narrow down the problem. When you've identified the problem you might then repost with more specific information (e.g. specific formulae) on what is associated with the problem so that solutions may be found.