When I searched for the answer I found this: http://inside-galaxy.blogspot.com/2013/12/samsung-galaxy-s3-how-to-fix-gallery.html.
It turns out that I had caused the problem, because in a flurry of turning off built-in apps, I turned off the "Paper Artist" app, which caused the crash on Gallery sharing.
When I Turned On the Paper Artist app, it fixed the problem.
Who would've thought that warning which stated "Turning off built-in apps may cause errors in other apps." would actually apply to anything?
Hope this is useful for anyone else with this issue.
My system for anyone who cares:
Software version: L900VPUCNE2
Hardware version: L900.09
Model number: SPH-L900
Android version: 4.4.2
Baseband version: L900VPUCNE2
Kernel version: 3.0.31-1561791, dpi@SWDD5716 #1
Build number: KOT49H.L900VPUCNE2
SE for Android statue: Enforcing, SEPF_SPH-L900_4.4.2_0016
Update (4/23/15): If the above strategy does not work, then you may want to check where your pictures are being saved and accessed.
I continued having problems with pictures on my phone, and the problem turned out to be a hardware one. The 64 GB microSD card I had installed was failing. I sent back the microSD card for a full refund, and bought a new 64 GB one (for cheaper, since the price has been dropping on memory!). Fixed a problem and made some cash, win-win.
