Connection to the K2.net server wsmrc2wsdmvm001 is invalid.

I've run into this problem while trying to submit a client page from an iframe. It works fine under a regular form. Could anyone tell me why ?
Thx.

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Connection to the K2.net server wsmrc2wsdmvm001 is invalid.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Exception: Connection to the K2.net server wsmrc2wsdmvm001 is invalid.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[Exception: Connection to the K2.net server wsmrc2wsdmvm001 is invalid.]
SourceCode.K2SmartForms.K2SmartForm.SaveData(K2SaveType SaveType, Object TriggerControl)

[Exception: Connection to the K2.net server wsmrc2wsdmvm001 is invalid.]
SourceCode.K2SmartForms.K2SmartForm.SaveData(K2SaveType SaveType, Object TriggerControl)

[Exception: Connection to the K2.net server wsmrc2wsdmvm001 is invalid.]
SourceCode.K2SmartForms.K2SmartForm.SaveData(K2SaveType SaveType, Object TriggerControl)
SourceCode.K2SmartForms.K2Button.OnClick(EventArgs e)
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +18
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
System.Web.UI.Page.ProcessRequestMain() +1292




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Version Information: Microsoft .NET Framework Version:1.1.4322.2300; ASP.NET Version:1.1.4322.2300