hard drive -- 230 GB used and 20 GB free (Been this way long before the problem started)
reboot -- I've been rebooting daily now, and the problem still persists.
apps -- Usually not more than 3 or 4. The problem persists even when I kill all other apps.
tabs -- This varies, but I've seen it happen with as few as 3 to 5 tabs.
The problem began about a month ago, and I'm wondering if there isn't some incompatibility with a recent Chrome update. I've looked into upgrading the OS to Yosemite, but after seeing mixed reviews, I don't really want to go that way unless I'm relatively certain that it will solve the problem.