Server Active Sync Errors dispite phones are syncing.

I just recently configured ActiveSync on our Windows 2003 Small Business Server, and even though it's working, I'm getting the following error message:

Unexpected Exchange mailbox Server error: Server: [server.domain.com] User: [username@domain.com] HTTP status code: [400]. Verify that the Exchange mailbox Server is working correctly.

We have 10 smartphones connected to OMA. 3 Palm Treo 750s and 7 ATT 8525s using Windows Mobile 5. OWA is working with no errors. and I'm using a 3rd party certificate. In the event log, there are two events with the same Event ID of 3005 logged for each user approximately 5 seconds apart. Then repeats every 6 minutes. The phones are set to sync when items arrive. Though it keeps checking on a regular basis. Dispite the error messages the phones are syncing everything with the exchange server. The problem is that I'm getting over 2800 critical errors a day. Kinda want to get that to stop. So far we are not noticing an impact on the servers performance.

If I go to http://www.domain.com/OMA from my workstation, I get the following error message:

"A System error has occurred while processing your request. Please try again. If the problem persists, contact your administrator."

&

the http address changes to http://www.domain.com/oma/(b40freaoe3rzsd55rgvwsf55)/oma.aspx

&

the following event error is logged:

Source: MSExchangeOMA          Event ID: 1503

An unknown error occurred while processing the current request:
Message: The remote server returned an error: (400) Bad Request.
Source: Microsoft.Exchange.OMA.ExchangeDataProvider
Stack trace:
   at Microsoft.Exchange.OMA.ExchangeDataProvider.OmaWebRequest.GetRequestStream()
   at Microsoft.Exchange.OMA.ExchangeDataProvider.ExchangeServices.GetSpecialFolders()
   at Microsoft.Exchange.OMA.ExchangeDataProvider.ExchangeServices..ctor(UserInfo user)

Message: Exception has been thrown by the target of an invocation.
Source: mscorlib
Stack trace:
   at System.Reflection.RuntimeConstructorInfo.InternalInvoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean isBinderDefault)
   at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at Microsoft.Exchange.OMA.UserInterface.Global.Session_Start(Object sender, EventArgs e)

Message: Exception of type Microsoft.Exchange.OMA.DataProviderInterface.ProviderException was thrown.
EventMessage:
UserMessage: A System error has occurred while processing your request. Please try again. If the problem persists, contact your administrator.
Source: Microsoft.Exchange.OMA.UserInterface
Stack trace:
   at Microsoft.Exchange.OMA.UserInterface.Global.Session_Start(Object sender, EventArgs e)
   at System.Web.SessionState.SessionStateModule.RaiseOnStart(EventArgs e)
   at System.Web.SessionState.SessionStateModule.CompleteAcquireState()
   at System.Web.SessionState.SessionStateModule.BeginAcquireState(Object source, EventArgs e, AsyncCallback cb, Object extraData)
   at System.Web.AsyncEventExecutionStep.System.Web.HttpApplication+IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Any help would be appreciated. Thanks.