I am not entirely sure, what is causing this problem for you, but if you
are using a GWorkspace version from SVN then you should be using GNUstep
gui and base from SVN as well.
The errors I'm getting is with the latest GWorkspace release, version
0.8.5, release last week! So theoretically it should work with the latest stable release of GNUstep, which is what I'm using. I'm not sure if maybe GWorksapce 0.8.5 is using functionallity that is only available in SVN, which is why I brought up that point.
Stefan