"Any-Program-Name" is not responding

Although I've used Linux for decades, I recently switched to Debian and have run into a problem. I am getting a message:

Quote:

"Any-Program-Name" is not responding. You may choose to wait a short while for it to continue or force the application to quit entirely.

In looking at the running processes, the one that is at the top is gnome-shell. Memory usage is low and nothing stands out. This is happening with all programs on the system.

I could really use your help in troubleshooting and resolving this.

TIA!