Just a guess ...
looks like you'r not closing the connections your requesting from the pool (e.g. in ejbLoad()/ejbStore())?
That could be the reason why the server does not respond ... it waits for a connection to be returned to the pool.
How are you using the connections?
What JBoss version?
I am using jBOss 2.4.3 with tomcat
You might want to stick with the XADataSourceLoader for jdbc access in jboss 2.4.x. I don't know of anything specifically wrong with the jca support in jboss 2.4.x but I think the XADataSourceLoader is a little easier to set up. If you want to use jca based jdbc access I recommend you use 3.0 rc3 or later.