Cannot edit NewForm.aspx of Custom List in Office Live Business Application in Sharepoint Designer

Question

I signed up for a Free officelive small business account. In the Business Application section, I created a Team Workspace application, in which I created a Custom List with only the Title column which is there by default.

I have Sharepoint Designer 2007 installed along with .net 2.0 SDK. According to one of the post, I increased the level of the Local Intranet to Full Trust. But even after applying all these steps, whenever I open my Office Live Business Application site in Sharepoint Designer and try to edit the NewForm.aspx file which is in the Custom List, the page shows an error:-

Error Creating Control - ShellContainer
This is not registered as safe.

The NewForm.aspx page of the Custom List is perhaps attached to the default master page originally.

Please help to resolve this issue and also guide me how to modify the NewForm.aspx page i.e. putting new controls in it, for e.g. If I click a radio button, a textbox should be displayed else remain hidden.

Regards,
AnsRaj