invoke dll in asp.net webservice(vc.net)

[Standist]

vs.net 2003
I create a webservice using vc.net.In the webservice invoked a method in a
dll from third party.
I compile and link the program without any error.But I got a error when I
debug it,I got the same error when I access the webservice through IE
directly.
The following is the error message:

line 196£º <add assembly="System.EnterpriseServices, Version=1.0.5000.0,
Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
line 197£º <add assembly="System.Web.Mobile, Version=1.0.5000.0,
Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
line 198£º <add assembly="*"/>
line 199£º </assemblies>
line 200£º </compilation>
source: c:\windows\microsoft.net\framework\v1.1.4322\Confi g\machine.config
line: 198

=== Pre-bind state information ===
LOG: DisplayName = xuweb
(Partial)
LOG: Appbase = file:///c:/inetpub/wwwroot/xuweb
LOG: Initial PrivatePath = bin
Calling assembly : (Unknown).
===

LOG: Policy not being applied to reference at this time (private, custom,
partial, or location-based assembly bind).
LOG: Post-policy reference: xuweb
LOG: Attempting download of new URL
file:///C:/WINDOWS/Microsoft.NET/Framework/v1.1.4322/Temporary ASP.NET
Files/xuweb/3f4a46fb/3e12f9c7/xuweb.DLL.
LOG: Attempting download of new URL
file:///C:/WINDOWS/Microsoft.NET/Framework/v1.1.4322/Temporary ASP.NET
Files/xuweb/3f4a46fb/3e12f9c7/xuweb/xuweb.DLL.
LOG: Attempting download of new URL
file:///c:/inetpub/wwwroot/xuweb/bin/xuweb.DLL.
LOG: Policy not being applied to reference at this time (private, custom,
partial, or location-based assembly bind).
LOG: Post-policy reference: xuweb, Version=1.0.2230.24024, Culture=neutral,
PublicKeyToken=null