Okay, I know this is OLD 2007, but some folks are still running it!
This is actually a two-part fix.
Fix the data source so it isn’t referencing the deleted fields
Fix the web part so it isn’t referencing deleted fields from the data source
Here’s the web part that is showing an error because field(s) were deleted from the underlying list (library).
The data source will not return any data because it is also messed up due to the deleted list fields.
You can find the datasource in the _fpdatasources folder.
Then you can edit it in XML or Text mode. You probably need to check it out first, or you won’t be able to save it!
Fix the data source. This involves finding the field in the data source XML that has been deleted. In this example, we have found <FieldRef Name="Scorecard"> that has been encoded (e.g. <). Delete it, and be sure you get all the correct text deleted.
Now you can see the data in the data source once again!
You need to fix the web part by finding the extra field(s) that are being referenced and remove them from the data source reference.
In the code view, find the <DataSources> tag and you can then locate the <datafields> section where the deleted list fields are still present. You need to remove them as shown above.
The server returned a non-specific error when trying to get data from the data source. Check the format and content of your query and try again. If the problem persists, contact the server administrator.