Absolutely, we'll let you know. We haven't heard anything yet.
If anyone else runs into this problem, that DevExpress thread is indicating that they have a fix for the issue (at least as a hotfix).
Unfortunately, we haven't had anyone from DevEx contact us. Conceptually there are some changes to how Identity was handled in 5.0 but I don't believe there's a difference within the 5.* line (Rob can confirm)
When importing tables from a vistadb5 db into XPO, the identity field of a primary key is not being recognized by XPO and hence XPO is not generating a suitable index value. XPO does recognize the Key but It is necessary to set the 'Is Identity' field to true or manually change [Key()] to [Key(true)]. Unfortunately, if regenerating the code using the XPO wizard, the wizard will then remove the 'Is Identity' or 'true' parameter.
The issue seems to only raise it's head when trying to save more than one table insert at a time.
Presumably an XPO issue but I wonder if it may also be an issue with VistaDB5 as I recall it was an issue with VistaDB4 but was fixed.