"GET EXTERNAL DATA" Feature Does not Work

From MS Excel 2007 (small business edition) I am unable to connect to any external data sources. This includes both Access files and SQL Server connections.

I have verified that I can link to those databases from another computer, and the main difference is when I click to connect, Excel actually appears to be trying to connect (and is then successful) whereas from my PC there is an immediate "Unable to Connect to Database" error in the case of MSSQL (for Access there just is no dialog that appears)

I have searched extensively for a solution on the web but have found no successful suggestion (including repair of office, dropping firewalls, changing connection parameters, file versions, etc..)

Does anyone have any idea what it could be? I went through the settings meticulously between the working PC and the non-working PC and made all the settings exactly the same, but nothing helps

Is there any sort of diagnostics I can use to see what's happening when an external data source is selected?

what, nobody?