Keyboard input problems switching between English and Japanese

Greetings All. I have been using the shortcut "command" and "spacebar" to change between English and Japanese input for the past year with no problems on my Mac (10.8.5). Then suddenly today when I type in English (and the English icon is showing in the top right corner of my screen), the characters suddenly change to Japanese and the English icon suddenly changes to either Japanese katakana/hiragana in the top right corner. I did not press the shortcut keys by accident, the language input just changed randomly. When I then use the shortcut to toggle back to English, it stays in English for a few seconds then reverts back to Japanese characters in the middle of typing.

Have browsed the forums for solutions but nothing has worked for me yet. Any ideas on how to fix this issue?

Thanks in advance for any tips!!

Burning Ember