Forgot Password - new exception error

We're just finishing off testing in v10 and our website forgot password function is throwing an error we've not seen before. 

The customer gets a custom error message, but their login is set to temporary in Tessitura, so we know teh call is getting through.

The email templates are in place, the API server is configured to send email and the API server can connect to the mail server

The exception is:

[18 Mar 2011, 13:55:20] 0.613501

/7610/registration-and-login/forgot-login-details.html Calling SOAP SendCredentials sSessionKey=QJNRY4X7CK1PBEQ1852PN73ESOUK

646X8F22EIIEGXJB3CV7NX3R0B14VEJAB303;sEmail=cjones@nationaltheatre.org.uk;iLoginType=1;bResetTempFlag=1;bUseToken=1;bGenerateNewPassword=;iTemplateID=54;

QJN

RY4X7CK1PBEQ1852PN73ESOUK646X8F22EIIEGXJB3CV7NX3R0B14VEJAB303

[18 Mar 2011, 13:55:20] 0.711513

/7610/registration-and-login/forgot-login-details.html Failed soap:Receiver

System.Web.Services.Protocols.SoapException: Ser ver was unable to process request. ---> System.PlatformNotSupportedException:

The HttpRuntime.ProcessRequest method is not supported by IIS integrated pipeli ne mode.

   at System.Web.HttpRuntime.ProcessRequest(HttpWorkerRequest wr)

   at Tessitura.WebAPI.Controls.LoginEmailPage.RenderPage(String pagePath, LoginCredentialData LoginCredentialData, String& body, String& subject)

   at Tessitura.WebAPI.EmailLogic.GetCredentialEmail(String sSessionKey, LoginCredentialData lcd)

   at Tessitura.WebAPI.Tessitura.SendCredentials(String sSessionKey, String sEmail, Int32 iLoginType, Boolean bResetTempFlag, Boolean bUseToken, Boolean bGen erateNewPassword, Int32 iTemplateID)

   --- End of inner exception stack trace ---

[18 Mar 2011, 13:55:20] 0.711652

/7610/registration-and-login/forgot-login-details.html Soap Error

System.Web.Services.Protocols.SoapException: Server was un able to process request. ---> System.PlatformNotSupportedException: The HttpRuntime.ProcessRequest method is not supported by IIS integrated pipeline mode.

   at System.Web.HttpRuntime.ProcessRequest(HttpWorkerRequest wr)

   at Tessitura.WebAPI.Controls.LoginEmailPage.RenderPage(String pagePath, LoginCredentialData LoginCredentialData, String& body, String& subject)

   at Tessitura.WebAPI.EmailLogic.GetCredentialEmail(String sSessionKey, LoginCredentialData lcd)

   at Tessitura.WebAPI.Tessitura.SendCredentials(String sSessionKey, String sEmail, Int32 iLoginType, Boolean bResetTempFlag, Boolean bUseToken, Boolean bGen erateNewPassword, Int32 iTemplateID)

   --- End of inner exception stack trace ---