I guess it could be the same problem as was reported for Chrome (https://issues.jboss.org/browse/RF-10835). Please review that issue and comment/vote on it if it is the same behavior also in IE9. To comment you need to login to Jira using the same account as on this page.
I can't reproduce the Chrome-issue, so I am not sure about that, but I think that my problem is a special IE-feature as it differs in the way it's happens just after the upload is completed.
even for the latest showcase (http://showcase.richfaces.org/) the fileUpload does not work with IE9. After some investigation, we propably found a solution or at least a workaround for this issue.
At first, it does not work in the ugly IE Quirks mode.
If somebody had set the compatible mode to "IE=8"
<meta http-equiv="X-UA-Compatible" content="IE=8" />
it doesn't work either. (I guess the most of the developer had set this, because of several CSS issues in quirks mode).
The trick is to set compatible mode to "IE=edge"
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
which means the browser-mode is IE-9 as well as the document-mode is IE-9 (but not quirks). (For IE-8, both will set to IE-8 automatically)
One can check this out for the showcase, too. (Use hot-key F12 to open the IE console.) By default the document-mode of the showcase page is set to "IE-8 compatible" (caused by meta-tag ..."IE=EmulateIE8"). If you change the document-mode to IE-9 (the browser-mode should already set to IE-9), the fileUpload works as expected.