Hello, my iMac is suddenly running slow. I've spent hours each day for the last two weeks on the phone with Apple suport. We have done a complete delete & reinstall of my OS, moved almost all files to the cloud or an external drive, but it is still slow. When we disable Dropbox, all is good and speeds are normal, so Dropbox is clearly the culprit. What has changed suddenly?? I don't want to use the web based version of Dropbox, but I cannot work a speeds that take 10 - 40 seconds for each click I do (who can?). My work PC is find and my iPhone and iPad are fine - they have no speed issues and Dropbox is running. Any ideas?
While we're at it, you could also have a look at the Help Center article which outlines why the desktop app may be causing high CPU usage on your computer, eventually slowing it down like you mentioned.