Hi cjchamber,

Please check your site application pool, you are using the .net framework 1.1, ajax uploader must use .net framework 2.0+.

By the way, this error is not causes by the uploader, it is causes by your web.config setting, .net framework 1.1 does not support System.Web.Extensions control, and you are using it in web.config, this is why causes this problem.

Regards,

Ken