I have other more serious problems with SDK2.3 (AVDs bust). I installed Ant builds OK to work with 2.2, and looked to see if Ant would build. My custom build.xml overloaded quite a bit of material in ant_rules_r3.xml, but still used it. I noticed that now it has been removed and replaced with main_rules.xml, which is slightly different. 'project.libraries' replaces 'android.libraries' for something. It's probably worth looking at the differences if your build.xml was based on ant_rules_3.
I will not look at it myself until my main problem is fixed.
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