Usually a block that won't purge is either inserted on a layer that's frozen or is nested in the definition of another block that's been inserted.
there are also a few reserved block names. You can't have a block called "*mspace" for example
In your case, it sounds like you're trying to replace an Xref with a regular block.
Try using the rename tool to change the name of the block that's causing the problem and see if you can then insert your external file.
That's exactly the problem...I can't find the block. You see what happened was I inserted the block the first time, but the document unit standard was all wrong. (inches instead of millimeters) So I opened up the block separately, and set it to the correct unit and re-saved. When I tried importing the block again, at first it seemed like nothing happened. It imported, but no block was showing at my x/y point. So I clicked undo a couple of times, and re-opened the block and checked everything...Tried it one last time, and that's when the nonsense started. That's why I was wondering if there is a why to search-select wayward blocks and delete them, cause I have absolutely no idea where it placed these blocks now in my drawing (or any remnants of the blocks)