the example below reproduces the problem when clicking a link during a long running page reload.
1. load the page (takes 2 seconds to complete)
2. reload the page [F5]
3. within the 2 seconds click the link
-> it will cause a "timeout error" because the desktop has already been removed

this get's additionally problematic in combination with a timeout page configuration

<session-config>
	<device-type>ajax</device-type>    
	<timeout-uri>/timeout.zul</timeout-uri>    
</session-config>

in this case the page reload does not complete and the timeout.zul is shown instead.

<zk>
    <div onCreate="org.zkoss.lang.Threads.sleep(2000)">
        <a label="click me after page reload [F5]" onClick=''/>
    </div>
</zk>

It is expected that the client engine does not sent ajax-events/requests to the server after the deskop has been removed.

A work around based on the zk.unloading variable could be implemented but is currently not reliable on all browsers (IE9/10 fail) due to issue ZK-2786