If a refresh of the page or clearing the client-side cache of images fixes the issue you’re encountering, then chances are that there is no server-side fix that is going to address the behavior you’re seeing. If the MOSS BLOB cache is involved (something you’ll have to verify), then I’m guessing that the web.config entry for the element on the web application in question specifies a max-age attribute value.

When the max-age attribute is specified, images and other BLOB resources that are served up to clients are passed back to the browser with client cacheability headers. In essence, the client will hold onto such images and resources until the amount of time specified by the max-age attribute has elapsed. Only after that amount of time has elapsed will the browser once again begin requesting the images or resources from the WFE. This is why a client-side solution, such as forcing a re-fetch or clearing the browser cache, is the only one that will actually get the browser to re-request the objects in question.

It’s been a couple of days since you submitted your comment. It’s common for the max-age attribute to be set to something like 12 hours. Your situation may even be fixed by now. If it’s not, and the max-age attribute is causing client-side caching, you should be able to use the value of the attribute to determine when things will clear up for you. The max-age attribute specifies a client-side caching duration in seconds, so divide the value by 3600 to determine how many hours objects will remain cached on client browsers.

Again, my hypothesis is entirely dependent on BLOB caching being enabled and a max-age attribute being set. If either of these aren’t in-play, then what I’m proposing isn’t what’s happening.

Good luck!