How to fix "System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.SharePoint.SPField.GetTypeOrBaseTypeIfTypeIsInvalid" ?

What?

I suddenly started to see an exception "An unexpected error has occurred" in our SharePoint 2010 site when I tried to access the site's landing page.

After digging through the logs, the exception actually is:

"System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.SharePoint.SPField.GetTypeOrBaseTypeIfTypeIsInvalid"
Google has returned no results for this unique exception.

The same exception has shown up on every page in the root site. All the sub-sites were doing fine.

Why?

It is obvious that this exception is specific to one site's pages library. All the pages in other sub-sites are working fine.

How?

I went into the pages library settings and then found that there are number of invalid fields.

I have also seen a strange link that appeared next to each invalid field that says "Delete this invalid field".

I went ahead and deleted all the invalid fields and woohoo all the pages in the root site are back and working properly.

Error: Only machine administrators are allowed to create administration service job definitions of type

Issue:

Tried to deploy a custom solution on a SharePoint 2010 farm from Central Administration > System Settings > Manage Farm solutions. I received the following error in the ULS logs.

Access denied. Only machine administrators are allowed to create administration service job definitions of type: Microsoft.SharePoint.Administration.SPSolutionDeploymentJobDefinition, Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c

Fix:

This fix only needs to be run on the machine that you are trying to deploy the solution on. However I would recommend disabling this “feature” on all SharePoint and SQL Servers in your farm.

Follow “to turn off UAC” http://technet.microsoft.com/en-us/library/cc709691%28WS.10%29.aspx

1. Click Start, and then click Control Panel.

2. In Control Panel, click User Accounts.

3. In the User Accounts window, click User Accounts.

4. In the User Accounts tasks window, click Turn User Account Control on or off.

5. If UAC is currently configured in Admin Approval Mode, the User Account Control message appears. Click Continue.

6. Clear the Use User Account Control (UAC) to help protect your computer check box, and then click OK.

7. Click Restart Now to apply the change right away, or click Restart Later and close the User Accounts tasks window.