The current org.hibernate.dialect.ProgressDialect does not support Sequences, as Progress 9.1 does. Following is a working Dialect for Progress 9.1 D Databases.
Please include it on the distribution (or update ProgressDialect).

package org.hibernate.dialect;

import java.sql.Types;

import org.hibernate.dialect.Dialect;

public class Progress9Dialect extends ProgressDialect {

@Override
public boolean supportsSequences() {
return true;
}

@Override
public String getSequenceNextValString(String sequenceName) {
return "select " + getSelectSequenceNextValString( sequenceName ) + " from SYSPROGRESS.SYSCALCTABLE";
}

@Override
public String getSelectSequenceNextValString(String sequenceName) {
return sequenceName + ".nextval";
}

}

Thanks.