I have been researching this issue and have found some very respectable institutions (Georgetown Univ., Univ of Wash School of Engineering, etc.) have had users of their website encounter and e-mail them as to why this is happening. Their responses are generally the same and their advice is to increase the browser cache size in one's Netscape preferences.
The header solution posed in the previous thread may be a viable alternative. I will darn sure give it a try.
Thanks,
Archer