Are you running custom firmware or anything? This is the first thing that comes to mind. If you are look up the issue on XDA - developers. The other thing is to make sure you have a good quality brand of SD card such as sandisk - you can get these dead cheap off amazon these days. Failing this (ie, if your software is stock and so forth) submit a support ticket with samsung and i'm sure they'll help you out.
Edit: holy shit it's kel, name changes confused me, how you goin' man?
Thanks for your input and suggestion for helping Llama, greatly appreciated! It is running all the stock/original firmware (no custom ROMs), just the fact that I've received at least 3 "Software updates" from Samsung in the past 3 weeks yet my Android version is still 4.2.2 JellyBean..
The only problem is, it seems to work fine now. I asked my dad if I could use his SD/SIM card reader to copy/move my data to my external drive (backup) then I erased my SD card data, inserted to my S4 and re-mounted it. it reformat the card in the phone and let me use it again. The only things that I found that was causing the issue was a certain "corrupt" app I had moved from my device storage to my SD Card. Since 4.2.2 JellyBean allows us to move some apps (that are compatible for it) to an SD Card. (which is a great feature!) - Overall the raging I actually did, I can't stress enough how much I raged...it works fine now.
A side from all of that, yes. It is me. (legally changed my name to Kyle though because I hated it) I am well, lots of work, moved to Cambridge from Leicestershire (the shithole) and am well. It's been a long time actually...still visited TGTAP as a guest to read some news every now and again, but I must be the only member to ever be banned from here and to have not tried to evade my ban with a second account... - this is still the only account I have ever registered on TGTAP at all.
Nice to know I'm still remembered! How are you? (PM me)