Thanks again everyone. I really appreciate your replies.
I've scanned the memory card thrice (Microsoft security essentials, AVG free and McAfee). Each time, it comes up that no threats are found and that all is OK.
But yet, each time the folder comes up as being empty. I've gone into the properties, and as best as I can tell, there are no hidden files. I've ticked the box that says to "show hidden files".
Whenever I put the memory card back in the camera, it tells me that there are 5 pictures remaining to be taken. If I take those 5 pictures, they are visible on the camera and they are also visible if I put the memory card in a pc/laptop.
The fact that the camera tells me that there are 5 pictures left to be taken on the memory card, tells me that the camera "thinks" that the other space on the memory card is already taken up with something. So, I tell myself that "something" (a virus???) is fooling the camera into thinking that the rest of the memory card already has something saved to it. But, what is that "something"? Some sort of virus I assume. That "something" seems to be telling the camera that the memory space is taken up, and the camera has been fooled into believeing it. However, when in a pc, the memory card is coming up as being empty. If I take the 5 pictures, they will show up in a pc.
When everything is OK, there are 3 folders that normally come up when I right click on the memory card's icon when I right click on the "computer" icon. Those 3 folders are "DCIM", "PRIVATE" and "MISC". I recognise those 3 folders, I know that they are and there's no problem there.
However, right now, there are 7 folders displayed. They are the 3 mentioned above, plus: ".fseventsd", ".Trashes", "autorun.inf" and ".-.Trashes. I don't recognise those 4 folders. Interestingly enough, they are "greyed" out, ie, they're not fully visible, it's like they're shaded or something. I can see that these 4 folders were created at the exact moment in time when the problem occured. However, the scans are not picking up these folders as a threat.
I'm tempted just to remove the folders to the recycle bin, but I suspect that the real problem is elsewhere. When I right click on these 4 folders, they're coming up as empty. I suspect that these folders may be some kind of shortcut, but I certainly wouldn't swear to it. However, the fact that these folders are "greyed" out makes me think that there's nothing to them, and they don't mean anything. It's what caused those folders to appear that is the problem, whatever that is.
Anyway, if anyone has actually read all of this, I thank you very much. I know that I can get this fixed for a sum of money, should I decide to do that. However, I want to learn what's caused this (this didn't happen because I pulled a memory card out of an sd slot without signing off properly), and how to correct it myself. I travel quite a bit, and ideally, I'd prefer how to fix these problems myself. Hence my desire to try and sort this out myself.
HELP.