>Something appears to have happened to my configuration in the last day or two. I can no longer run my web app (using F5 or CTRL-F5). The browser shows up but then rather than rendering the ASPX in the browser, the file downloads as if it were an FTP site. Then a clone version of the ASPX file appears in HTML form . . . and the browser closes.
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>I have re-loaded and re-configured IIS and tried starting over with a simple one form solution but still cannot get it resolved.
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>Anyone have any experience in this?

I have not had this situation but you may want to verify that your start page is what it is suppose to be.