Hi since upgrading from the previous version to version 3.0 when I delete an image from a product in the admin area I get the error:  "The requested url did not return json".  
Since I got this error, the image from my home page slider has also stopped working.  When I edit the slider the reference is there, but it no longer shows.  
I followed the update instructions to when doing the update, and didn't get any errors

Now when I look in the logs I see heaps of errors as follows.

What has gone wrong and how do I fix it?

Regards,

Scott

Error  No slider picture found with the specified id  5/25/2013 2:23:14 PM  View
Error  No slider picture found with the specified id  5/25/2013 2:23:14 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 2:23:03 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 2:23:03 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 2:22:31 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 2:22:31 PM  View
Warning  Shipping (Australia Post). Please enter a valid Service code.  5/25/2013 2:09:37 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 1:45:52 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 1:45:52 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 1:41:05 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 1:41:05 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 1:22:56 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 1:22:56 PM  View
Error  The controller for path '/test/aspnet/test.aspx' was not found or does not implement IController.  5/25/2013 1:10:27 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 1:09:52 PM
Error  Value cannot be null. Parameter name: picture  5/25/2013 1:09:52 PM  View
Error  No product picture found with the specified id  5/25/2013 1:09:29 PM  View
Error  No product picture found with the specified id  5/25/2013 1:09:29 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 1:08:49 PM  View
Error  Value cannot be null. Parameter name: picture  5/25/2013 1:08:49 PM  View
Error  A public action method 'SubscribeNewsletter' was not found on controller 'Nop.Web.Controllers.NewsletterController'.  5/17/2013 5:51:25 AM  View
Error  The controller for path '/bundles/scripts/bapkh5ik10iwi95kvshooptcueyz-5tbiayp0qfiae41.js' was not found or does not implement IController.  5/15/2013 7:09:05 AM  View
Error  The controller for path '/Content/smoothness/jquery-ui-1.8.17.custom.css' was not found or does not implement IController.  5/15/2013 7:09:03 AM  View
Warning  Shipping (Australia Post). Please enter a valid Service code.  5/11/2013 9:49:18 PM  View
Warning  Shipping (Australia Post). Please enter a valid Service code.  5/11/2013 8:56:47 PM  View
Error  Error while running the 'Keep alive' schedule task. The remote server returned an error: (500) Internal Server Error.  5/11/2013 8:18:51 AM  View
Error  Error while running the 'Delete guests' schedule task. An error occurred while executing the command definition. See the inner exception for details.  5/11/2013 8:16:47 AM  View
Error  Error while running the 'Keep alive' schedule task. The remote server returned an error: (500) Internal Server Error.  5/11/2013 8:13:51 AM  View
Error  Error while running the 'Keep alive' schedule task. The remote server returned an error: (500) Internal Server Error.  5/11/2013 8:08:50 AM  View
Error  Error while running the 'Delete guests' schedule task. An error occurred while executing the command definition. See the inner exception for details.  5/11/2013 8:06:46 AM