Failed to create Java Project...

I have an existing Java project with an ant build scrip, build.xml. I
tried to create an Eclipse project by using the "Java Project from
Existing Ant Buildfile" wizard. However, every time I select the
build.xml file in the "Ant Buildfile" field, there is an error

  The file selected is not a valid Ant buildfile

However, I can use ant to build using the same build.xml file. My
questions:

  1. Is there a more detailed error message from Eclipse about what's
     wrong with the "build.xml" ant file I specified in the New
     project wizard?

  2. How is the Ant/Eclipse integration happen? Which ant executable
     does Eclipse use? Could it be that my problem is actually a
     configuration problem?

Here are my environments.

OS: Linux river 2.6.22-14-generic #1 SMP Tue Feb 12 07:42:25 UTC 2008
i686 GNU/Linux

Eclipse: Version: 3.2.2
Build id: M20070212-1330 ('Ubuntu' version: 3.2.2-3ubuntu3)

Java: Java HotSpot(TM) Client VM (build 1.6.0_03-b05, mixed mode,
sharing)

Ant: Apache Ant version 1.7.0 compiled on August 29 2007

Thanks in advance,

Estro