I recently started using boost for drupal on a current project which seems to have amplified one of IE's annoying habits, namely not emptying the cache when I tell it to. Sometimes no matter how many times I tell IE to empty its cache, it just hangs on to the old version of a page.
As far as boost's role in this, perhaps it is related to an Etag setting or something like that, I don't know yet*, but IE's cache being sticky is not a new problem. However, I just happenstanced across a workaround: If you click the compatibility view button twice (looks like a broken page icon ) it magically empties the cache for the page you are looking at. Make sure to wait a moment for the page to load between the first and second click… when you are done the compatibility mode button should not be blue.
This button tells IE8 to act as if it is IE7, it is designed to help old sites that don’t work right in IE8. The first click puts it in IE7 mode, the subsequent click switches it back to IE8 mode and presto.. the cache is cleared for that particular page.
*Note that I am comparing boost's creation/expiration timestamps in the source code of the page in IE8 vs FireFox and Chrome. In case you were thinking that I might be getting confused by what is cached on the server vs browser level :)