Server Error: Validation of viewstate MAC failed

Some users experienced this specific “viewstate” error when changing windows or tabs. There are a few technical reasons for the issue. If you do experience this “viewstate” error, we have a few steps for your to follow.

Figure 1: Screenshot of the error.

Resolution

The quickest way to resolve the issue is deleting the cookies from the EIOBoard site then logging back into the website.

For Chrome users

1. In the Address Bar, next to the EIOBoard address you will see the lock icon.
2. Click on Cookies
3. In the new pane, select the folder of site Cookies
4. Click Remove to delete all the Cookies for the EIOBoard site
5. Click Done
6. Close the tab, or return to the EIOBoard Login page.
7. Your EIOBoard web application will prompt you to enable Cookies for the site.
8. Login as you normally would

For Firefox users

There is a shortcut to delete the cookies for a website within the Lock icon.

1. In the Address Bar, next to the EIOBoard address you will see the lock icon.
2. Click “Clear Cookies and Site Data..”
3. Click “Remove”
4. Reopen the tab
5. Login as you normally would

For Internet Explorer users

The only option is to delete all site cookies. There is no option to delete one site’s cookies.

1. Select Tools Gear
2. Select “Internet Options”
3. On the General tab, click “Delete…”
4. Uncheck “Preserve Favorites website data” and check “Cookies and website data”
5. Click Delete.
6. Reopen the tab to EIOBoard
7. Accept the Cookies Enabled dialog box
8. Login as you normally would

Conclusion

The web application stores a session token that does not always validate against the machine key of the intended web server. We will make the appropriate accommodations in the near future.

Details in the body of the Error:

Server Error in ‘/EIOBoard’ Application.  Validation of viewstate MAC failed. If this application is hosted by a Web Farm or  AutoGenerate cannot be used in a cluster.  See http://go.microsoft.com/fwIink/?LinkID=314055 for more information.  Description: An unhandled exception occurred during the execution of the current web reauest. Please review the stack trace for more information about  Exception Details: System .Web_HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that er  See httpwgo.microsoft.com/fwink/?LinklD=314055 for more informaton. 

Error:  An unhandled generated during the regarding the origin the  Stack Trace:  [ViewStateException: Invalid viewstate.  Client IP:   Port: 52189  Referrer: https :  Path: /EIOBoard/Login.aspx  User-Agent: Mozilla (KHTML, like  ViewState:  [HttpException (Ox8æø4æ5): Validation of viewstate failed. If this application is hosted