Boolean problem

I experience many problems needing to union objects
See pics attached
Pic 1 the error message I get
Pic 2 before union
Pic 3 after union

this is a very simple model that I use to test options before going for the full modeling
I have always had problems with union and intersection.

System win 7 , 4 GORAM, nvidia 1 go Blender r57644



Well, I have some problems with booleans not working like they should now and then. Maybe there is a bug?