Solr 4.0 indexing NoSuchMethodError

[elisabeth benoit]

Hello,

I've just installed Solr 4.0, and I am getting an error when indexing.

*GRAVE: java.lang.NoSuchMethodError:
org.apache.lucene.util.CodecUtil.writeHeader(Lorg/apache/lucene/store/DataOutput;Ljava/lang/String;I)Lorg/apache/lucene/store/DataOutput;
    at org.apache.lucene.util.fst.FST.save(FST.java:311)*.

Does anybody know what I've done wrong?

Thanks,
Elisabeth