The compiler is case sensitive. So be careful of your spelling and capitalization:
(image1Loader vs. image1loader <-- see any difference there???).
removeChild doesn't unload anything, it only removes it from the display list. The loaded item will still be in memory, ready to display again with the next addChild.
To remove items from memory altogether, use the unload() method of the Loader class. Or, if you are going to be loading mutiple items one at a time, consider just using the same loader instance again. No need to unload what's there, just use it to load something else, and the former thing will automatically be unloaded.