Hello Jack, my name is Dan.
I will do my best to help you, the only stupid question is the unasked one.
I do not use Spring Cleaning and that is one of the reasons why, it is unpredictable.
I suggest a bit of maintenance that may bring things back online.
One is to repair permissions, this PDF will explain how.
After doing that I suggest a safe boot.
To do a Safe Boot, restart and before the first chime press and hold the 'Shift' key.
Wait until you see the Apple logo and the spinning gear appear, then let go.
It can take as long as 20 minutes to load, so please be patient.
When the login screen appears it will say in red on the login window 'SafeBoot'.
Now login and give it a few more minutes to finish loading.
Try doing whatever it was it was giving you the problem. If it works then probably the problem is solved, so restart normally.
If the problem persists then restart normally also, other fixes will need to be done.
Make certain that you restart normally after doing this because some things will not work while in safe mode.
A pram reset would not be out of order.
To do a PRAM reset, you need to restart your machine and hold down these 4 keys.
‘Option’, ‘Command (Cloverleaf or Apple)’, ‘R’ and 'P'.
Keep them down until you hear 4 startup chimes, this is the sound your Mac makes on startup.
If you have a wireless keyboard then the procedure is a little bit different.
Use the very same keys but wait until the first chime and immediately press and hold those keys. I recommend getting your fingers ready because timing is critical.
This resets all of the system buses on your computer, USB, FireWire, display, ethernet and your keyboard/mouse/trackpad.
This will correct many faults but not necessarily yours.
This is not guaranteed to fix the problem but it will certainly do a lot of good for your machine.
You may have missed the Firefox plist. I suggest using spotlight to find any remnants.
Let me know how you make out.