Try clearing cache and cookies then try again. Your browser is probably still trying to use the HTML5 uploader.
Cookies IE7
To clear your cookies in Internet Explorer 7, click on "Tools". It's in the top right corner of the browser. Then select "Internet Options". That's going to open a new window with some options. Make sure that the "General" tab is selected. Then click on "Delete..." under the Browsing History section. That will bring up another window. Locate the "Delete Cookies..." button and click on that. That will remove all the cookies from your browser.
Cache IE7
To clear your cache in Internet Explorer 7, click on "Tools". It's in the top right corner of the browser. Then select "Internet Options". That's going to open a new window with some options. Make sure that the "General" tab is selected. Then click on "Delete..." under the Browsing History section. That will bring up another window. Locate the "Delete Files..." button and click on that.