Hi, I hope someone can help with this one.  I've just installed saleslogix 7.5 service pack 4.  We had been on Sp2, and since I had a number of issues with the differencing tool not really working, I decided to take a different tack, and just install a vanilla out of the box saleslogix build and apply service pack 4.   That bit seemed to work well, the project builds, and deploys with no problems.  

I had bundled all of our SP 2 customisations into architect bundles, but there are lost of issues with the platform not building, so I am left with manually adding everything back in. I am in the middle of doing that just now, but whenever I try to add a new entity using the entity wizzard, the platform refuses to build.  I get a warning like

WARN  - C:\Users\hobbse\AppData\Roaming\Sage\Platform\Output\interfaces\IAccountAlias.cs(45,16):'Sage.Entity.Interfaces.IAccountAlias.Id' hides inherited member 'Sage.Platform.ComponentModel.IComponentReference.Id'. Use the new keyword if hiding was intended.

And then the errors 

ERROR - C:\Users\hobbse\AppData\Roaming\Sage\Platform\Output\implementation\AccountAlias.cs(460,24):The type 'Sage.SalesLogix.Entities.AccountAlias' already contains a definition for '_Id'

INFO  - AccountAlias.cs(82,24): (Location of symbol related to previous error)

ERROR - C:\Users\hobbse\AppData\Roaming\Sage\Platform\Output\implementation\AccountAlias.cs(461,31):The type 'Sage.SalesLogix.Entities.AccountAlias' already contains a definition for 'Id'

I figured this out now.  When you use the wizard to add an entity it names the primary key property as ID.  If I re-name the property to AccountAliasID then it builds OK without errors.  I guess that it is overriding a base entity class with an ID propery, however the tool that generates the interface does not know how to properly override this.  You would think Sage could have fixed this by 7.5 service pack 4, but I guess we will have to wait a bit longer for that.

You might want to start with a sp4 backup instead of upgrading the from 750.

there are several sp3 API changes and a DLL you need to remove from the VFS that are hurting you.

What i'd do is:

create your sp2 differencing bundle and apply that to the 754 vanella backup

load another 754 backup into a parrellel vfs folder on disk and use a tool like Beyond Compare to enable side by side file comparisons.

Also look at the sp3 API change guide thats on the support site.