Ok, i see and i can reproduce this:
1) Create a new file
2) Create a long line within this file (lets say at least 2000 characters...
3) Save the file
4) Close the file
5) Open the file again
6) The scroll bar will not be updated and display a default with. If you use the scroll bar to go to the end of the line it will crop of. You still can use the arrow keys to go to the end.
Also using the end key works...
To circumvent this bug, you can select the line and press the "end" key on the keyboard. This will bring you to the end of the line, and will update the scrollbar...