john,
I think it's not a server issue. Most likely it's client side issue.
When you testing local and server, are you using the same browser?
Are you using AjaxUploader version 3.0?
Which version of .NET framework are you running on the server?
Can you try the following example and get back to me?
1. If Ajax Uploader detects SilverLight is installed on your PC, It will use the SilverLight solution.
2. If Ajax Uploader detects Flash is installed on your PC, It will use the Flash solution.
3. If Ajax Uploader detects Iframe is supported on your Browser, It will use the Iframe solution.
4. For downlevel browsers, Ajax Uploader will render as default ASP.NET upload control.
Hope it helps.
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