Today while working with latest STS on Ubuntu 9.10 I observed that it simply doesn’t work properly. While importing projects, nothing happened. Later I found out that it has to do with a bug on Eclipse 3.5 for which a workaround is available on Ubuntu and it works fine.
Set the following environment variable before you run STS.
export GDK_NATIVE_WINDOWS=1
Details of the bug are available here.