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

I am not sure if all of you have run into the following error in the last couple of weeks:

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)

It turns out is it caused by a Microsoft Service Update. (KB2844286 for Server 2008 R2 and KB2844287 for Server 2008)

RESOLUTION: You will need to uninstall the update from your WFE and APP servers.

Control Panel > Unistall a program > View installed updates (on left) > Uninstall the KB (Under the Microsoft Windows section)

Here are the bulletins about the patch:

KB2844286
KB2844287

There a few MS forum posts about this:

“Unable to display this Web Part” error message after patch KB2844286

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

I am not the only one that has a write up on this:

ISSUE: KB2844286 Security Update on SharePoint 2010


NOTE: One point to add. I was not able to get my web parts working again without rebooting my farm. Yes, SharePoint hates me and would not just allow an IISRESET.