I've recently completed my first DNN upgrade by upgrading my test site from 7.0 to 7.3 and have errors related to telerik. The script tag to call  /telerik/Web.Ui.WebResource.axd return an error "Failed to load resource: the server responded with a status of 500 (internal Server Error) and subsequently this results in another error being generated by the next line of code because "Sys is not defined" Sys should be set by telerik script. There are other js errors also that I believe are all related to the telerik file not loading. The site displays although some CSS is not correct and I can't use the host menus because javascript is broken. 

There are telerik tags in my web config that recognize an upgrade was performed and has a different version number than production. The telerik dll files in the bin folder are also newer than the production files so they were definitely upgraded. 

Any ideas or help is greatly appreciated.