When you have a Select box with a value change listener in a tab set, theValueChangeEvent's getOldValue method returns null, rather than the actual old value. If you remove the tab set, this issue does not occur.

Using the supplied test case, when you change the select box in the top example (not in a tab), it works as expected - the list gets a new entry, displaying the old value to the new value.

But when you try the same in the bottom example (tabs), you see that the old value is always null. And if you press the submit button, you see that value change events keep firing, even though you didn't make a change. Lastly switch the tab away and back. You'll see the tab go back to the default value rather than maintain it's state. (this works fine in the official SP1 release).

This issue may depend on the fix for Jira 1993 which was applied to the 1.7 branch on March 26.

http://jira.icefaces.org/browse/ICE-1993