OWA not working

I have a new Exchange server 2010. OWA and active sync are broken. When i try "https://mail.03design.com/owa". I get this error:  Server Error in '/owa' Application.

The following event is recorded in the application event log

Log Name:      Application
Source:        ASP.NET 2.0.50727.0
Date:          12/8/2012 11:16:13 AM
Event ID:      1310
Task Category: Web Event
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      DARTHVADER.zero3.lan
Description:
Event code: 3007
Event message: A compilation error has occurred.
Event time: 12/8/2012 11:16:13 AM
Event time (UTC): 12/8/2012 5:16:13 PM
Event ID: 844559a94afc4187ba5e6fd32cf10807
Event sequence: 3
Event occurrence: 1
Event detail code: 0

Application information:
    Application domain: /LM/W3SVC/1/ROOT/owa-1-129994605721269009
    Trust level: Full
    Application Virtual Path: /owa
    Application Path: C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\owa\
    Machine name: DARTHVADER

Process information:
    Process ID: 4068
    Process name: w3wp.exe
    Account name: NT AUTHORITY\SYSTEM

Exception information:
    Exception type: HttpCompileException
    Exception message: (0): error CS0006: Metadata file 'C:\Windows\assembly\GAC_MSIL\System.Web.Mobile\2.0.0.0__b03f5f7f11d50a3a\System.Web.Mobile.dll'could not be found

Request information:
    Request URL: https://darthvader.zero3.lan:443/owa/
    Request path: /owa/
    User host address: fe80::5d4c:ccf3:239d:da2e/owa
    User: 
    Is authenticated: False
    Authentication Type: 
    Thread account name: NT AUTHORITY\SYSTEM

Thread information:
    Thread ID: 1
    Thread account name: NT AUTHORITY\SYSTEM
    Is impersonating: False
    Stack trace:    at System.Web.Compilation.AssemblyBuilder.Compile()
   at System.Web.Compilation.BuildProvidersCompiler.PerformBuild()
   at System.Web.Compilation.ApplicationBuildProvider.GetGlobalAsaxBuildResult(Boolean isPrecompiledApp)
   at System.Web.Compilation.BuildManager.CompileGlobalAsax()
   at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled()
   at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters)


Custom event details:

Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="ASP.NET 2.0.50727.0" />
    <EventID Qualifiers="32768">1310</EventID>
    <Level>3</Level>
    <Task>3</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2012-12-08T17:16:13.000000000Z" />
    <EventRecordID>10246</EventRecordID>
    <Channel>Application</Channel>
    <Computer>DARTHVADER.zero3.lan</Computer>
    <Security />
  </System>
  <EventData>
    <Data>3007</Data>
    <Data>A compilation error has occurred.</Data>
    <Data>12/8/2012 11:16:13 AM</Data>
    <Data>12/8/2012 5:16:13 PM</Data>
    <Data>844559a94afc4187ba5e6fd32cf10807</Data>
    <Data>3</Data>
    <Data>1</Data>
    <Data>0</Data>
    <Data>/LM/W3SVC/1/ROOT/owa-1-129994605721269009</Data>
    <Data>Full</Data>
    <Data>/owa</Data>
    <Data>C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\owa\</Data>
    <Data>DARTHVADER</Data>
    <Data>
    </Data>
    <Data>4068</Data>
    <Data>w3wp.exe</Data>
    <Data>NT AUTHORITY\SYSTEM</Data>
    <Data>HttpCompileException</Data>
    <Data>(0): error CS0006: Metadata file 'C:\Windows\assembly\GAC_MSIL\System.Web.Mobile\2.0.0.0__b03f5f7f11d50a3a\System.Web.Mobile.dll'could not be found</Data>
    <Data>https://darthvader.zero3.lan:443/owa/</Data>
    <Data>/owa/</Data>
    <Data>fe80::5d4c:ccf3:239d:da2e%11</Data>
    <Data>
    </Data>
    <Data>False</Data>
    <Data>
    </Data>
    <Data>NT AUTHORITY\SYSTEM</Data>
    <Data>1</Data>
    <Data>NT AUTHORITY\SYSTEM</Data>
    <Data>False</Data>
    <Data>   at System.Web.Compilation.AssemblyBuilder.Compile()
   at System.Web.Compilation.BuildProvidersCompiler.PerformBuild()
   at System.Web.Compilation.ApplicationBuildProvider.GetGlobalAsaxBuildResult(Boolean isPrecompiledApp)
   at System.Web.Compilation.BuildManager.CompileGlobalAsax()
   at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled()
   at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters)
</Data>
  </EventData>
</Event>

By the way, the System.Web.Mobile.dll file does appear in the following path as well as some other places.

C:\Windows\Microsoft.NET\assembly\GAC_MSIL\System.Web.Mobile\v4.0_4.0.0__b03f5f7f11d50a3a\System.Web.Mobile.dll

How can Ifix OWA?

Thanks,

Charles