Flashing folder icon appeared once after changing Macbook hard drive About 2 weeks ago, I updated my late 2011 Macbook Pro hard drive to a Crucial MX100 solid state drive. The drive installation and data migration went fine with no issues, but today I found the computer in a state where the screen just showed the "flashing folder" icon indicating an issue with the main boot disk. I restarted the computer in recovery mode and verified the disk, and Disk Utility said the disk was fine, with no issues. I then rebooted into Mac OS X (Yosemite 10.10.2) as normal and the computer is working fine.

Is there any reason why this would suddenly happen like this? Are there any hard drive related settings I should change on my system now that I have changed to a solid state drive from a magnetic drive?
This could have been a situation where the PRAM somehow lost the startup disk settings. If you reboot holding Command+Option+P+R and wait for the startup chime (or two) that will reset the PRAM and might fix the issue.

What you did was exactly right, however, as there might have been disk corruption or some other sort of disk problem. Unfortunately disk utility isn't as verbose as many would wish. Other disk utilities like Diskwarrior, TechTool Pro or Drive Genius might give you a more detailed report And even a freeware SMART utility might give you info on the health of the drive that Disk Utility won't report.

In other words you might be fine and this was a random occurrence (Murphy was a computer engineer...) or it could be the sign of an impending failure.

I would check it out further, and back up my data.