Error occurred in deployment step 'Activate Features': Operation is not valid due to the current state of the object

I got this error "Error occurred in deployment step 'Activate Features': Operation is not valid due to the current state of the object " while attaching a event reciver using Visual Studio 2010 in SharePoint. Just for some more information I am attaching the event receiver to a SharePoint 2010 publishing web site. And the event was WebProvisioned.
When I checked the web.config file I have added the Assembly as MyPageLayoutEventReceiver. Though this is same as the assembly name, but was throughing error.
When I change the Assembly name to $SharePoint.Project.AssemblyFullName$, that worked. So my elements.xm file will be as like below:

<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
  <Receivers >
      <Receiver>
        <Name>EventReceiver1WebAdding</Name>
        <Type>WebAdding</Type>
        <Assembly>$SharePoint.Project.AssemblyFullName$</Assembly>
        <Class>MyEventReceiverLayout.EventReceiver1.EventReceiver1</Class>
        <SequenceNumber>10000</SequenceNumber>
      </Receiver>
      <Receiver>
        <Name>EventReceiver1WebProvisioned</Name>
        <Type>WebProvisioned</Type>
        <Assembly>$SharePoint.Project.AssemblyFullName$</Assembly>
        <Class>MyEventReceiverLayout.EventReceiver1.EventReceiver1</Class>
        <SequenceNumber>10000</SequenceNumber>
      </Receiver>
  </Receivers>
</Elements>