Plone 2.5 Browser-specific Issues Understood (Not Solved)

I'm administering a few Plone 2.5 sites under Windows.  Sometime over the past two months, I noticed that when I tried to use Kupu, the rich text editor, to edit the content type Rich Topic, the body of the topic text was blank.  No editing was possible.  After looking into this further, I was reminded that this feature (which is now standard in Plone 3 and 4) was provided via a third party "product" (Plone team's notion of a plug-in of sorts) simply called RichTopic and I think originated with Jon Stahl.  In later versions, the feature is referred to as rich text fields on collections.

But nothing had changed in the site configurations -- except, of course, the browsers, which had undergone numerous upgrades since the original Plone 2.5 deployment.  After painstaking testing, I was able to determine that the symptoms persisted in Firefox 3, Safari (to the extent that Safari Win could be used for testing), and IE 7 and 8. In Opera, I was able to see the HTML, but the editor wasn't using its toolbar properly so I was reluctant to use Opera to update the content.  Here's the surprise:  SeaMonkey (v2.0.1) which I use as an HTML editor, worked fine.

Updated 8 January 2010 It's some complex caching problem, as pages visited for the first time for a browser work properly.  After repeated edit visits, they stop working.

Perhaps it was my browser plugs, or security, or the Plone skin being used -- unclear.  But perhaps this will save someone else a little time.  My "solution" will be to ignore this problem and to upgrade to Plone 3, though that is not a trivial process.