If the Global Overview page doesn't contain any data, please check the following:

For Internet Explorer on Windows Server 2008 and 2008 R2, ensure that the SQL Monitor website has been added to the list of allowed local intranet sites:

1. Go to Tools > Internet Options > Security.
2. Under Zones, select Local intranet.
3. Click Sites (For IE 8, click Advanced > Sites).
4. Add the SQL Monitor website. (This should be pre-selected.)

For all browsers: Check that Javascript is not disabled on your browser.