building av Qrc4 file destroys sconsign.dblite file
After adding a Qrc4 build into our somewhat complex build the whole sconsign.dblite is destroyed. So whenever we build, we get complete rebuilds, and explanation is that no previous build information is found.
After some experimenting I managed to get rid of this problem. What I needed to do was puzzling enough to comment out the prefix=... part of the qrc_builder, after this fix and a rebuild the builds behave again.
If this is an issue with SCons itself or the Qt4 tools I don't know. But hopefully it is worth to take a look at.