
After installing SDL and using it as the platform, the game runs flawlessly on Debian Linux. That makes a lot of sense now, that X11 was treating the keystrokes akin to a text editor. Thank you so much for your help, I appreciate it a lot.
Also thank you hpg678 for the article, it's really interesting. I had never thought of the concept of time-based movement... definitely something I'll try to implement.