Null Reference Exception While Executing the Webpart

In SharePoint some times after the deployment the Webpart may shows the below error.

If we look into the log, the following error message will be logged:

Error while executing web part: System.NullReferenceException: Object reference not set to an instance of an object.   

at System.Xml.Xsl.XslCompiledTransform.Load(MethodInfo executeMethod, Byte[] queryData, Type[] earlyBoundTypes)   

at Microsoft.Xslt.STransform.GetCompiledTransform()   

at Microsoft.SharePoint.WebPartPages.BaseXsltListWebPart.LoadXslCompiledTransform(WSSXmlUrlResolver someXmlResolver)

at Microsoft.SharePoint.WebPartPages.DataFormWebPart.GetXslCompiledTransform()   

at Microsoft.SharePoint.WebPartPages.DataFormWebPart.PrepareAndPerformTransform(Boolean bDeferExecuteTransform)

Solution:

This is because of one windows update. The update Windows KB2844286 is causing this error.

So uninstall the Windows KB2844286 update. Then the webpart will work.

To Uninstall: Control PanelàPrograms And Featuresà View installed updates àSecurity update for Microsoft windows Windows KB2844286 (under Microsoft Windows category)àUninstall