Error - Server Error in '/Reports' Application - system.drawing.dll

Hi,
I've got a small issue - I can't access my report server anymore!
Everything was working beatifully, up until we restarted the server
last night.
Now when I try to access the site i get the following:
Configuration Error
Description: An error occurred during the processing of a configuration
file required to service this request. Please review the specific error
details below and modify your configuration file appropriately.
Parser Error Message: Assembly system.drawing.dll security permission
grant set is incompatible between appdomains.
Source Error:
Line 253: <add assembly="System.Web.Services,
Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
Line 254: <add assembly="System.Xml, Version=1.0.5000.0,
Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
Line 255: <add assembly="System.Drawing,
Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
Line 256: <add assembly="System.EnterpriseServices,
Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
Line 257: <add assembly="System.Web.Mobile,
Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
Source File:
c:\winnt\microsoft.net\framework\v1.1.4322\Config\machine.config
Line: 255
The server hadn't been restarted since report services was installed.
As far As I'm aware, nothing else has been installed since.
Has anyone got any suggestions?
Thanks,
SarahSolved!!!
The problem related to security permission.
As it is set up for internal use only, we made the following change to
fix the problem.
In services, World Wide Web Publushing - added permisssion to allow
serice to interact with desktop.