Ryan, this is a known issue. It is caused by adding an event to a control from the Extension Library. What happens is the "eventHandler" tag is incorrectly associated with the "xe" namespace rather than the correct "xp". At present, the workaround is to fix this in the Source view as follows:
<xe:djTextBox id="djTextBox1">
<span style="font-family:courier new,courier,monospace;"><<span style="color:#008000;"><strong>xp</strong></span>:eventHandler event="onBlur" submit="true" refreshMode="partial" refreshId="refreshPanel"></span></div>
<span style="font-family:courier new,courier,monospace;"></<span style="color:#008000;"><strong>xp</strong></span>:eventHandler></span></div>
</xe:djTextBox>
This has been raised and addressed, see SPR (DEGN8LFE64).