I still have all the errors mentioned before. And I have no ideas anymore. I tried small thread_cache_size (8) and big ones (2000). I tried to increase connections (up to 2000) on mysql-site. I tried lots of configurations for the mysql-ds.xml. But I get the same errors every time. Perhaps its really a problem of the Windows XP + JBoss 4.2.3 + MySQL 5.1 combination. Any suggestions? I will try JBoss 5.0.0. Perhaps he will be nicer to me. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4224266#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...