I just updated to Minecraft 1.7.3 & 1.7.4 and was playing on creative singleplayer. I tried using the "/gamemode" (without quotes obviously) command to switch to survival mode. As I started typing, I used the Tab feature to finish the command. As I typed I typed "/ga", then used Tab to finish out the word gamemode. However, when I pressed Tab, it finished the command to "/game" instead of "/gamemode". I had not experienced this problem in any previous versions.