[Zope] IE 5.0 and Basic Auth

I have been fielding all kinds of complaints about erratic behaviour with Zope Basic Authentication and the common denominator seems to be IE 5.? I know nothing about windows, etc. Would someone be able to enlighten me as to why every version of netscape I've tried works properly, and IE 4.0 works properly, but IE 5.0 won't even allow me to manage a site?? TIA jb