TFS WebAccess Error: [HttpException (0x80004005): Unable to validate data

We were getting the following error while setting our TFS2010 Web access. Sharing the solution which worked for us, might be useful for you.

Error:

[HttpException (0x80004005): Unable to validate data

Solution:

1. On App Tier server, goto C:\Program Files\Microsoft Team Foundation Server 2010\Application Tier\Web Access\Web.
    (Please make a copy of Web.config, just in case you need the original file later.)

2. Edit the Web.config file in notepad.
3. Search "machineKey" in Web.config file.
4. Replace the <machineKey> section with following.
<machineKey validationKey="AutoGenerate,IsolateApps" decryptionKey="AutoGenerate,IsolateApps" validation="3DES" decryption="3DES"/>
5. Save the Web.config file.
6. Restart the Microsoft Internet Information Services (IIS) service.