Black box appearing, unable to see artwork, unable to save document.

I was drawing, clipping and adjusting my artwork when suddenly a black box appeard for a few seconds, and when i zoomed out all artwork disappeared. When marked in the layers channel, i'm able to se that everything is there, but i cannot really see it. then, after zooming a bit in i can see everything, but when trying to start edit, i'm unable to do any changes other than delete. when trying to save the document, an unknown error occurs, wanting me to save the document to contact support - but the problem is that im unable to save... i managed to export as a png, but first try non of the lines were visible. second try i removed visibility on all other layers than the painting lines, and then the lines were visible, but the black box were too (see attached image). Im really scared to loose all my artwork and hope to get some help from you guys.