I think it is probably a cacheing (sp.) issue, and I played with some of the seting in IE with no positive results. I have not seen any problems with 5.1.2, but I also have not been working on anyhting locally, recently.
It also might be an issue with Apache's configuration. Recently I had some problems with Apache delivering some images. The system was and Apache/Resin/Oracle solution running on Sun hardware. Because we really did not have the time to trouble shoot Apache, the first thing we tried was eliminate Apache and use Resin to serve the flat HTML content while functioning as the Servlet runner. It worked like a charm.
So that makes me thing that it may be a some sort of problem with Apache and maybe a time-out sort of situation. I'll post the fix if we figure out what the problems was on the above config.
-Jason