The server could not complete your request. Contact your Internet service provider or Web server administrator to make sure that the server........

soap:ServerServer was unable to process request. ---> A Web Part or Web 
Form Control on this Web Part Page cannot be displayed or imported because 
it is not registered as safe on this site. You may not be able to open this 
page in an HTML editor that is compatible with Microsoft Windows SharePoint 
Services, such as Microsoft Office SharePoint Designer. To fix this page, 
contact the site administrator to have the Web Part or Web Form Control 

configured as safe.

Solution:

1. Open the site, for example http://mossportal/site/default.aspx
2. add "?contents=1" to the end of url, like this: http://mossportal/site/default.aspx?contents=1
3. You have a Web Part Page Maintenance and if you have some web part error delete it
4. Open the page with SharePoint Designer and all work correctly