Your mouse not working correctly in Marathon on PC is hugely frustrating. Here are some fixes to the known bug you can try. Update: Bungie has released a patch to the Server Slam client that appears ...

If you use a wireless mouse, its batteries might be low. Replace the batteries and check if this helps. If this does not work, you can use a wired mouse. The driver of your gaming mouse might have ...

Bungie is working on a real fix, but for now, try this.