a4j:support does not allow comma separated list of event. It should be only one even name there.
In general, you can have several a4j:support attached to the same component. However, in your concrete case, onclick and onchange are duplicate each other. Use only one of them.
P.S. I do not see the reason for having <a4j:region immediate="true" >. You tried to use exorcism to make the code working, did not you?
Many thanks for immediate answer!
You're right, it was some exorcism for this case. :)
And I didn't removed it. :(
Sorry for bothering you.