Sys is undefined error ScriptResource.axd line 2

We are getting the error Sys is undefined error ScriptResource.axd line 2 in the Administration section when trying to view product details. If I connect to the hosting site from development env I can view everything fine. However if I login to the admin section through hosting account we see this error. We just moved to production, please let us know how to resolve the issue.

We are using version 1.4

I had this problem before on a website I was developing...not with nopCommerce though.  The problem was that the URL Rewrite module does not work well with Ajax control toolkit.  This may be your issue too.  I never did find a solution for it...I just took away the URL rewrite module.

sys is undefined means the ajax scripts were not loaded.

it is generally caused by a wrong version of ajaxtoolkit or corruption in the libraries during compiletime.

the way to correct it is to remove the ajaxtoolkit, make sure you add the right version again and recompile.

don't forget to clean your solution (delete the file in Bin directory if you have to).

recompile again and you'll be on your way.

The issue arises when I changed the IIs setttings for our 404 pages to our default page. Once you do that the problem starts if you don't do custom errors for 404 everything works fine. I spend some time on that last night. Hope this will be useful information for others.

Like deccks says it appears to be an issue with URL rewrite