If you're having issues when saving the game, there are a few things we'd suggest trying to see if you can get this process to work successfully.
First of all, if within a save game try going to FM -> 'Save As'. When prompted to save, try saving to a different location than default (such as the desktop) and see if the game saves. If you can save there, then there is a problem with where your default Sports Interactive files are pointed and we'd suggest reading our FAQ on How to Change the Folder Location
If you're still having issues or the game crashes whilst saving, we'd suggest as a first step uninstalling and reinstalling your graphics card drivers. Once this is done, try again. If you're still having issues, try lowering the 'graphics quality' of the game via the in-game preferences (say from Very High/High to Medium) and see if you encounter the same issue.
As a final step if you still have issues, sometimes anti-virus programs can interfere with how the game saves, so make sure to configure your anti-virus so that it won't conflict with FM or Steam. You may have to uninstall and reinstall FM as suggested in the like above during this process to make sure it works.
If nothing above works, please raise an thread on our Crashes and Technical Issues forum stating exactly what you've tried so far and a member of our support team will try to help.