Tad,
I know I got this working with the original production version of SQL Server Express. Right afterwards the GUI management component for SQL Server died and could not be resurrected, so I gave up on that database installation, and thus the EA component.
In response to my suggestion that explicit support for SQL Server 2005, Sparx says that people have EA running there. But, nothing in the way of explicit support as yet.
There is a Service Pack 1 release of SQL Server 2005, at least for the Express edition. I've downloaded, but not yet done the upgrade on my development machine. Nor have I attempted another connection with EA.
My suggestion is that you report this via the Sparx support page. If Sparx has an answer that works, please post the work-around here. If I do the upgrade in the next little while I'll try another connection and let you know what happens.
David
PS: I know this does not solve the problem at hand, but if you are looking for a very current EA repository at little cost, try Oracle 10g Express. I got it working with EA the first time, but following the Oracle 9i instructions (with a little common sense thrown in). Not bad if you ask me, and I'm a Microsoft fan from way back...