Hi misty4,
Thanks for reaching out about this issue. Not being able to click where you need to without an error can be a pain. I'd like to do what I can to help you out.
Based on what you've described about not even being able to log out or do a backup, you may not be able to do the following troubleshooting steps either, however if you can, please give them a try.
Start with re-sorting the customer list. It may seem like a simple thing, but sometimes it jogs things back into working order and resolves these kinds of issues. To do this, go to View in the top toolbar and click Re-sort List. Click OK on the prompt that warns you it will put your list to its original order. Once it's done, try clicking again to see if the error still pops up.
If it does or if you're unable to try that troubleshooting step, the next step is to check your company file for data damage. The article walks you through the steps of determining if there is data damage on your company file and how to resolve it if there is.
In the event you're still having trouble, give the phone support team a shout at 1-877-772-9158. Pro and Premier agents can troubleshoot with you at any time as they're available 24 hours a day, 7 days a week. Enterprise agents can help from Monday to Friday between 9 a.m. and 8 p.m. EST. With a screen share session and other troubleshooting methods, they'll help you get back on track.
I hope that helps!
