I have just found that the use of uppercase/lowercase has changed in 7U21.
We have been running with the codebase notation like this: codebase="http://SERVER:port/folder/file.jnlp" since Java 1.4.2
In 7U21 I get a dialog pr. jar.
If I change to: codebase="http://server:port/folder/file.jnlp " the dialogs are not shown.