During racking my brains for almost the whole day crawling to the root of this problem I suspected many things.
However, the solution turned out to be missing slf4j-log4j dependency in maven :)
<dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> <version>1.5.8</version> </dependency>
How did I find this? Put a break point into org.jboss.seam.persistence.HibernateSessionFactory, and discovered that Hibernate did not bootstap properly without this lib and the real exception had been swallowed. What a shame )
Anyway, I'm happy now )
Wish everyone not to come across similar weird issues )