Icon take it no more!

First off permit me to apologize for the horribly, horribly bad pun. I just thought that it might catch someone's attention.

Anyway, I have had this problem for some time now. If I decide to change an individual icon, when I save the package, several icons will then display the incorrect icons. For ex.: .png images may all display an .ini file instead of .png files. And if I go and then try to correct the .png files other files become messed up and it just kinda snowballs. Why is this happening and more importantly what can I do to correct it? The biggest headache is that I sometimes have to re-download and re-install the icon package to get everyting back to normal. This can be a ngihtmare when you're stuck using dial-up. Very frustrating. Any help will be appreciated.