I have the following error when I host my chart on I64 W2K8/IIS 7. it is totally fine in my Vista 32 bit/IIS7.

 What is the issue here? I have register the dll to GAC and restart the server and still unable to fix this issue.

Line 57: <add assembly="Xceed.Chart.Graphics2D, Version=4.2.100.0, Culture=neutral, PublicKeyToken=BA83FF368B7563C6"/>

Line 58: <add assembly="Xceed.Chart.GraphicsCore, Version=4.2.100.0, Culture=neutral, PublicKeyToken=BA83FF368B7563C6"/>

Line 59: <add assembly="Xceed.Chart.GraphicsGL, Version=4.2.100.0, Culture=neutral, PublicKeyToken=BA83FF368B7563C6"/>

Line 60: <add assembly="Xceed.Chart.Standard, Version=4.2.100.0, Culture=neutral, PublicKeyToken=BA83FF368B7563C6"/>

Line 61: <add assembly="Xceed.Chart.UIControls, Version=4.2.100.0, Culture=neutral, PublicKeyToken=BA83FF368B7563C6"/> 

I also have issue with Line 64: <add assembly="Xceed.Compression.PPMd, Version=3.7.8516.10220, Culture=neutral, PublicKeyToken=BA83FF368B7563C6"/>

Did I install the package correctly? or maybe I did the GAC incorrectly? or is this a known issue with 64 bit OS and/or W2K8 ? 

This is because the assemblies must be run within 32 bits applications.  So to run them on a 64 bit server, you must set the server to run applications as 32 bits.  Here is more information from Microsoft on how to do this on IIS :

http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/405f5bb5-87a3-43d2-8138-54b75db73aa1.mspx?mfr=true

The other option is to not use 3D charts and PPMd compression.