Mouse jumps around when using DOSBOX

Not 100% sure this is the problem, but autolock often causes mouse issues in DOSBox. So try setting it to the opposite of whatever it currently is:

• In your dosbox.conf file, look for a line setting autolock=false and remove the line (or change the false to true).
• Or, if no line with autolock exists, add one with autolock=false.

If you are trying to run dosbox in a virtualbox Ubuntu host, I had the same issue and it was driving me crazy. The mouse would just get stuck in a corner and wouldn't move except to the other corners. Here's the solution I found:

Make a text file and put this in it:

#!/bin/bash
export SDL_VIDEO_X11_DGAMOUSE=0
dosbox

Save it on your desktop or somewhere else, right click on it and put a check where it say "allow to execute as application". Run the file and the mouse issue will be fixed.

I know that the original poster has already resolved their issue, but for everyone else hitting this from Google: for me this was an issue with VirtualBox's mouse integration. To fix it, disable your virtual machine's mouse integration by right clicking on the mouse icon in the bottom right-hand corner (second icon from the right).

After this, the mouse should respond to the sensitivity setting in DOSBox.