I work on a large application with a Qt 4 GUI. On one of my Windows' PCs I get a cursor drifting away when this application is running. The cursor starts moving on its own in some direction (top to bottom or diagonally) steadily, linear, without changes of the direction. I can move it with my mouse but it continues the drift once I stop resist it. This starts in a random moment of time: it can start right at the moment I run the application or after several minutes of a normal work.
Honestly, I don't have a clue how to start with debugging such an issue. Can anyone be so kind to give me a clue on where to start, a place to stand so I can move this stone?
To make it clear, I have access to the source code of the application, I can compile a debug version of Qt libraries as well, if there is such a need.