Reference component not found

[ama55]

Dear All;
i am new to the .net framework. i am creating a sharepoint sequential
workflow.
The problem is that i can not modify the workflow at at the design
page. no items are displayed, instead and error is.
the error is:
Error 1 The designer cannot process the code at line 47:

this.onWorkflowActivated1.SetBinding(Microsoft.SharePoint.WorkflowActions.OnWorkflowActivated.WorkflowIdProperty,
((System.Workflow.ComponentModel.ActivityBind)(activitybind1)));

The code within the method 'InitializeComponent' is generated by the
designer and should not be manually modified. Please remove any
changes and try opening the designer again.

and here is the warning:
Warning 2 The referenced component 'Microsoft.SharePoint' could not be
found.

Thanks for your help

best regards
ama55