In reply to apforrest:
As it's a product designed for purpose, the Beal marker shouldn't have chemically changed the rope, and, assuming it's otherwise undamaged, it's very unlikely that the rope's strength has been compromised - so the issue is probably just the handling, whether it passes easily through a belay device. I would manipulate that section of rope until it softens up - in front of the telly, maybe
.... that's not to say that I, or anyone else on here, can 100% guarantee the safety of your old rope, of course. How old is old? These days there are always some pretty good deals on entry-level, single ropes to be found - you can get close to £1 per metre if you shop around.