This is an old problem that I know I filed a ticket on years ago. The dialog for Cross References attempts to display the entire path to the file in a pop-up menu, regardless of how long the file path is. At the same time, in an attempt to display the long pop-up menu item, the width of the dialog box is adjusted, apparently without limit. The width can easily exceed the width of the screen. The user can, with patience, drag the dialog box so that the right edge is visible and can thus click on OK or Cancel or Apply, but attempts to drag the right side of the box to the left and thus make the box narrower, fail, as resizing is not allowed. This behavior persists even if the current file path is not long, but a previously opened long file path remains as a pop-up option. (Why do old file names live in this menu anyway?)
This isn’t how things are supposed to work. A long string for a pop-up menu item is supposed to be truncated and terminated with an ellipse, …, and hovering over the truncated string should show a tooltip with the entire string. Jerry