Hi Trent,
the problem I've seen on Olivier's computer is a weird mapping, that I'm not able to reproduce on any one of mine...
for some historic reasons (VFP background, but that is really old ages), in its SQL server, he handles integer through Decimal (N,0) columns.
And in the BO mapper, directly on the tables (no DDT at this step), all these Decimal columns are mapped to Int32!
Of course, when running the app, there is an invalid cast error bubbling from the ODBC layer.

Having the same database on my local SQL Server, the same SF version, I'm unable to reproduce this error. Going on its development machine, I see this error in BO mapper. I'm going here and there with this error for a couple of days, still not understanding the origin.

I can't find which part of the SF source code could set this incorrect mapping, and I suspect a bad SQL Native Client. What piece of code would help you to help us?