The puzzle one in the mine just gives loot.
Have you gone through Maxos temple yet? There is a required series of platforms there, though not timing critical as in the Depleted Ore mine puzzle. If you meant the platforms in Barnabus' cave for the lava jumping puzzle, or the key in the High Halls mine, you must be past there already.
It may help if you remap some keys (I switched jump to the Numpad 0 key, for example, to be beside the arrow keys).
A controller should make things easier for jumping, as well, if available.
You would need to use something like AntiMicro
to map mouse movement to a gamepad stick, etc (it has included stick profiles for mouse, WASD, arrow keys, etc).
To avoid a problem with the camera resetting, you may need to start the game with the controller unplugged, and plug it in afterwards.
If needed, in the Developer Mode version of the Developer's Cut release, you could morph into a small flying creature (ladybug) to get through some of the jumping sections. When morphing back to the 'Player' character model, the male model is used; you'd have to visit an illusionist to switch genders, if you are playing a female character (there is one in the battle tower dining hall).