So erm... don't shoot me. I've not given up on Blackthorne just yet (esp as we still don't have actual inline editing in SB, at least not in a particularly useable way). But Windows 10 is scuppering my plans 
I upgraded from win 7 a couple months ago, not used blackthorne since, and have just gone to open it and got the standard sql switch database window. Everything's correct (comp name, sql instance, db name, uses windows auth) but trying to connect just gives error "Could not validate this file". "SQL Server (SQLEXPRESS)" service is running, and restarted. I saw a mention of SQL Server Agent but the only on I have is for the sixbit db. Could be a permissions issue I guess - I recall something like that years ago, but now the old message boards are gone I can't search my old comments.
So erm... any tips? Should I finally resign myself to full SixBit useage (not that I really sell on eBay these days anyway)? Or is it as simple as enabling a random service?
EDIT: MS SQL Server Management Studio 2008 is giving me the following error when trying to open BTData 
.
===================================
The database BTData is not accessible. (ObjectExplorer)
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Program Location:
at Microsoft.SqlServer.Management.UI.VSIntegration.ObjectExplorer.DatabaseNavigableItem.get_CanGetChildren()
at Microsoft.SqlServer.Management.UI.VSIntegration.ObjectExplorer.NavigableItem.RequestChildren(IGetChildrenRequest request)
at Microsoft.SqlServer.Management.UI.VSIntegration.ObjectExplorer.ExplorerHierarchyNode.BuildChildren(WaitHandle quitEvent)
EDIT 2: This don't look good 
Microsoft SQL Server Express Edition with Advanced Services
9.0.5000 SP4
AMITY\SQLEXPRESS
An exception occurred while executing a Transact-SQL statement or batch.
Server is unavailable
Server is unavailable
Also, don't have permission to create a new user to give permission to access the database to tell if it's a permissions issue. 