Hi John
Suspect that you've locked one or more of the axes. i have TC 20, and if you go to the bottom RH corner of the screen there are 3 boxes which show the X, Y and Z positions for the cursor. Beside each one is a tick box which locks the position of the cursor for that axis – make sure that you haven't accidentally ticked one of them.
Other things to try -.
1 Look under 'modes / snaps' on the drop-down menus and make sure that you haven't selected 'ortho', as that will allow the cursor to move at right angles only.
2 With the line tool selected, right click and select 'local snap' – you may have selected ortho here – deselect it and all should be ok.
Please let us know what you find – good luck
Roger