What causes this problem is blocks being referred to inside other blocks (nested). And since leaders and dimensions create anonymous blocks, they can show up without you even knowing about it.
In pre-2004 (not sure about 2002), you should be able to just run the purge command a few times, but you shouldn't have to save to get it to work.
In 2004, in the purge dialog box, click the purge nested items box, and it will purge all blocks, including those nested inside other blocks.
Also, in the future, please let us know what software you are running so we can better help you, as different versions may have different solutions