WSP builder doesn't add all dll's to the wsp package

I have had tremendous problems trying to get WSP Builder build correctly and include all dll's in the WSP package (and SafeControl settings in the manifest.xml).

Now it finally seem that I have found a solution:

1. Delete old assemblies from the GAC first
2. Clean solution
3. Rebuild solution
4. Build WSP

This seems to work every time now. :-)