>Hi,
>I often get a bug when I try to open form in DesignMode like
>
>[A]MKS.GoliathNet.Windows.Controls.ApplicationControls.mks_dictionary_ctrl_RepositoryItem cannot be cast to [B]MKS.GoliathNet.Windows.Controls.ApplicationControls.mks_dictionary_ctrl_RepositoryItem. Type A originates from 'MKS.GoliathNet.MKSApplicationControls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' in the context 'LoadNeither' at location 'C:\Users\gavrikov\AppData\Local\Microsoft\VisualStudio\9.0\ProjectAssemblies\gcr2240f01\MKS.GoliathNet.MKSApplicationControls.dll'. Type B originates from 'MKS.GoliathNet.MKSApplicationControls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' in the context 'LoadNeither' at location 'C:\Users\gavrikov\AppData\Local\Microsoft\VisualStudio\9.0\ProjectAssemblies\d18samlt01\MKS.GoliathNet.MKSApplicationControls.dll'.
>
>Waht is that.. what means those d18samlt01 folders and why it casting classes between? what there happens?

Seems like a cacheing issue. See:
http://west-wind.com/weblog/posts/628455.aspx
Have you applied this : http://support.microsoft.com/kb/969612/ ?