I have attempted to find a solution for my problem at several seperate occasions, but since I don't actually have a name that descibes the problem, searches have resulted in very little. Searching "invisibilty" and the like has only given information about the layer functions and opacity, which as far as I can tell is not the problem.
Thus, my final resort is simply to join this forum and flat out ask for help.

I am using Inkscape as a free alternative to Illustrator in order to trace lineart in order to ease the coloration process further down the line. I already started this particular lineart in illustrator, but my trial period ran out and forced me to start using Inkscape instead. I imported the .AI file, and it works in every way except for one.
It would appear that some form of box (originaly A4 proportions) is surrounding the image. The problem with it is that it appears to filter all lines that are outside of it when the image is imported. The lines are not removed, but instead made invisible for some reason. They are still there, and they are selectable, only not visible. I have already fiddled around with the "box" itself, changed the proportions to a size larger than the image, but that still doesn't change the invisible line that is seemingly filtering my lineart.
Here is an image of where the "line" starts filtering:


As you can see, it doesn't affect anything within the borders of this invisible box, even if the line continues outside of it, it just makes it invisible from that point on.
I have tried selecting the line and painting it, and it doesn't work. I have selected the line and draged it to within the borders of the "box", and it becomes invisible once it enters that area, but it turns invisible again if it leaves it.

I can still draw new lines outside of the box without any problems. I can also import other images and resize or move them outside of the borders without any problems. It's solely the lines that were imported as the original image that can't go outside of these boundries without becoming invisible. Playing around with layers does nothing, and neither does playing with the opacity.

Any help would be appreciated.

often imports from AI come clipped or masked. You will need to remove it; it usually doesn't serve any function anyway. I think you might be able to find enough info on how to do this on this forum?

What exactly is it that I need to find information about how to do? As I said in my first post, the biggest problem is that I have no idea what the actual problem is, so searching for a solution has been absurdly hard. My onlys tags have really been "invisible" and "border", and that doesn't give much.
All I managed to find on both google and this forum when it comes to clipping was people talking about how to make clipping and the like in Inkscape. I was unaware that there was a clipping problem, but even so, I still have no idea what I'm looking for.

What exactly am I looking for, and what is it meant to do? Could you in any way elaborate on how exactly my problem works? Currently, I have no idea what to do.

It sounds like druban is suggesting un-clipping or un-masking. I'm not familiar with AI imports into Inkscape, so I'm not sure about this part. You might be able to find out if the object(s) are clipped or masked by selecting, and looking at the status bar. It will say what kind of object it is. Once you know, you can select the object, then go to Object menu > Clip > Release or Object menu > Mask > Release. Once you do that, there probably will be a previously not visible object (the clipping or masking path) that will need to be deleted. Although again, I'm not familiar with this type of situation, so I'm not sure if the clipping path (or masking object) will show up or not. Just keep your eyes on the object as you click Release.

Here's the manual info on Clipping and Masking. http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Clip.html Clipping is usually used like cropping. It's technically not the same as cropping, but it's used like cropping. In raster graphics programs, masking is often used to create shading. I forget exactly how it works, but black areas are transparent (don't affect what's underneath) and white areas change color (affects whatever is underneath). Or it might be the other way around. I don't use masking much, and couldn't answer any technical questions about how it works in Inkscape. I'm sorry not to be able to explain it. Oh, but you might also look and see if clipping and masking is addressed in the Quick Guide. There's a link in my forum signature.

I hope that helps at least a little