An announcement from the Fedora announce list:
With the update to a 2.6.18-rc based kernel, Xen requires some more effort to get to working. Given that Xen is one of the big features for Fedora Core 6, trying to ship the second test release (and thus the feature freeze) without Xen seems like a less than ideal situation.
Therefore, after discussion within the Fedora Board, we have decided to slip the freeze for test2 until Xen is working again with current kernels. Based on current estimates, it looks like this should hopefully be Monday, 24 July. We'll continue to provide updates as more information is available.
Jeremy