Have you tried restarting your machine?So why is this often the first recourse for an IT help-desk type? Simply because, 7 out of 10 times*, it works.
At the very least, restart the program that you are having problems with and preferably restart your machine. Why? Imagine your computer as a worker in an office. You give it a job to do and it quite happily gets on with it. Then you give it another job. No problem. And you carry on piling jobs onto it which, for today's workhorses, is no big deal. However, there comes a point where one piece of paper gets lost. It's here somewhere but there are twenty piles of paper scattered all over the desk. Everything grinds to a halt while this one piece of paper is searched for. There is a quicker way of doing this. Clear the desk of all paper and start the jobs again, one at a time. The paper will turn up, or be recreated.
Now it's not a watertight illustration, but it gives you an idea of what the issue is. I hate to break it to you but computers are dumb creatures. So if one part of a process goes walkabout, the entire system could grind to a halt while the software tries to untangle itself. In the long term, it's often easier to clear the decks, as it were, and start again. Restarting will close every program and file, shut down the operating system and basically allow it to find itself, in a non-profound sense.
Save what you can. Know what you've done and what will need doing again. Make a coffee. Black, no sugar. Thanks.
*79% of statistics are made up on the spot