Audacity won't open file,

Yesterday I was editing a file and as I was working Audacity gradually became slower and slower until it finally crashed. Now, Audacity goes nonresponsive and has to be force quit every time I try to open that particular file. Any idea why this might be happening and how I can fix it? The .aup and the data file are next to each other on my desktop. I’ve rebooted my computer. I have the most recent version of Audacity. It’s never done this before.

I would obviously really like to avoid losing the work I’ve done on this project!

How long is the show? How many tracks? Your description feels like you’re running out of environment or possibly straight drive space. You should File > Export the work as a perfect quality WAV file, but you will not be able to do that if you have a long or complex show.