I doubt it is a problem with memory as I run a machine with only 16Mb total and it works fine.
You say you are running in dos, by that do you mean a dos box under windows or do you mean you BOOTED to dos (c: prompt)? If it is the former, that is your problem. You need pure dos to run run TCNC. Also make sure your have absolutely no add ins in your autoexec.bat or config.sys files. The way it is compiled, doesn't need emm or any of that. The ONLY driver I load is mouse.com and that is at the time I load TCNC