They can succesfully upload files but deleting seems to be the problem. Is this an IIS or .NET Framework policy issue and can this be changed by support?
Description: The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file.
Exception Details: System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.SecurityPermission, mscorlib, Version=188.8.131.52, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.