System.IO.FileLoadException: Access is denied

[Gopi]

Hi,
I am using the System.Reflection.Assembly.LoadFrom
(strAssemblyPath) method to load an assembly in my web
services, which has got only Basic authentication set in
IIS and Identity is set to true in web.config.

I have given full access (ACL) to every one on the dll and
the parent folder which contains this dll. And I have
given full permissions on this dll and parent folder to a
domain user, credentials of which being passed to Web
service. But Web service throws me the following exception

System.IO.FileLoadException: Access is
denied: 'MyBoard.dll'.

If I make that domain user as part of domain admin group,
then this exception doesn't occur. I don't want that user
to be part of the domain admin.
Can any one pls let me know the reason for this?

TIA
-Gopi