Netscape crashes with a bus error when the following occurs: I have my preferences set to not download any mail over a certain size (over 50k) I recieve a mail wanting a return receipt. Whether I accept or decline doesn't seem to matter. I click the link to download the full attachment. Netscape seems to create a duplicate mail containing the full downloaded attachment. Upon completion of the download, the "new" mail asks the same question about accepting or declining the return receipt. After the answer, netscape crashes with bus error either way.
You might try 4.76 to see if that solves the problem for you. Unfortunately, we don't have access to netscape's source, so we can't really fix this problem. Reporting this to netscape at: http://help.netscape.com/forms/bug-client.html may help.