The machine often stops booting until an external interrupt (keypress, mouse move) wakes it up.
AMD Phenom II X6 1090T, Asus M4A89TD PRO/USB3
Debugging narrowed it down to non-working workaround for APIC timer breakage in AMD C1E (erratum #400).
I proposed a patch upstream:
This issue has been proposed when we are only considering blocker
issues in the current Red Hat Enterprise Linux release. It has
been denied for the current Red Hat Enterprise Linux release.
** If you would still like this issue considered for the current
release, ask your support representative to file as a blocker on
your behalf. Otherwise ask that it be considered for the next
Red Hat Enterprise Linux release. **
For some reason I can't reproduce the freeze now.