Glad it helped, Felix!

Now it worked fine.
There were two problems here. As the solution has two projects, and one was depending on the other, when compiling both together, the .net framework was reseting to 2.0 in one of them. I´ve deled one of them and compiled the dll and then adedd the other one and worked fine.
But the issue was the one you were telling me
Regards!!!

I´ve did it but still the same issue:

Under your project properties, go to the Advanced Compile Options. Check your application "Target Framework". If you have it set to "Client Profile", change it to the full framework version.

I did not change anything, not in the sample file, nor in the SF itself.
Anyway I tried changing the .Net framework version to 3.5 and making the project a release, but evrething is still the same.
I´m using the libraries located at C:\Program Files (x86)\MicroFour\StrataFrame\Assemblies
Other sugestions
Thanks

Hi Felix.
Check if this could be your case:
http://forum.strataframe.net/FindPost30699.aspx

I was working around the sample data installer class And I´m having something that make me to give up.
Im using VB 2010
When I load the sample I have to reload the strataframe references.
Then everything appears to be fine, no error in the source code, nothing wrong at all
When I Rebuild the solution the MicroFour.StrataFrame.DBEngine seem to be unload and all the classes regarding this object give me error. If I load again the library evereything becomes to normal, but if I rebuild, again happends the same.
so What I did is remake all the project from scratch but happends exactly the same.
There must be something regarding my develop environment but I cant figure out what.
Some help please?