If you save your patch using the name of one of the existing Max objects, this object can not be instantiated anymore. For example, if you save your patch as message.maxpat, you will lose messages functionality in all of your patches. I fully understand why this happens, but this happens again and again (ask the support guys!), because it is impossible to memorise all of the Max object names.
I think user-friendly environment should give user a warning in case if he is trying to save the patch using one of the reserved names.