Reinstalling RM2K3 itself may help. If you can, post what operating system you're using as well. I recently installed RM2K3 on a new laptop with Windows 7, and had no text issues.
Also, look in the program's folder (Program Files/Enterbrain/RPG2003), and then go into the Font folder. Make sure the font is there. For me, it's a font called RMG2000, inside a folder titled Eng Font. If it's there, try installing it(double click, select install). If not, let me know and I'll upload it for you.
For reference, it should look somewhat like this: