IE8 is suddenly refreshing entire window on page change/refresh

After my Vista 64 was updated via Windows Update to include upgrades to .NET, graphics, etc. (basically, pieces of Windows 7, I believe) Internet Explorer 8 has been doing something very annoying on many web sites. It's very noticeable on some sites I've built.

开发者_StackOverflow中文版When the page is refreshed or another page - even from the same site - is loaded, the entire window refreshes itself as though it was loading for the first time; very disruptive. It's really noticeable on sites with darker backgrounds such as http://www.northridgecommunitychurch.com, but it's also noticeable here on the stackoverflow.com site.

Is anyone else noticing this? Can a developer do something - or stop doing something - to restore the smooth page transitions I was seeing until a couple of days ago?

Thanks in advance.

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Just to add to my question, there is no trace of this problem in Firefox or Opera. Only in IE8, and only there in the past day or two.

Nevertheless, if anyone has any ideas for code modifications that might overcome the problem before clients start complainining....

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You'd see much less flicker if the site was using HTTP Expires & Cache-Control headers properly; see http://www.fiddler2.com/redir/?id=httpperf