By regex search and replace, this patch resets obvious self-blockers after the update,
back to the original package name.
--- /usr/lib/portage/pym/portage/update.py	2012-10-13 18:39:58.103791174 +0100
+++ update.py	2012-11-07 21:39:18.548708950 +0100
@@ -56,6 +56,9 @@
 				else:
 					return "".join(matchobj.groups())
 			mycontent = re.sub("(%s-)(\\S*)" % old_value, myreplace, mycontent)
+			# revert self-blocks (#367215)
+			mycontent = re.sub("!" + new_value + "(\\s|$)", "!" + old_value + "\\1", mycontent)
+
 	elif update_cmd[0] == "slotmove" and update_cmd[1].operator is None:
 		pkg, origslot, newslot = update_cmd[1:]
 		old_value = "%s:%s" % (pkg, origslot)