Posted: 11/06/2013 at 12:06
Sorry Hogroast, late again. Hope I'm not too late. Does the sap smell sour, like vinegar? Is there an orange discoloration in the bark? In that case bacterial cancer is most likely, which fidgetbones suggested above. Infected areas under bark or branches are usually sunken and oozing sap. Google for photos to get an impression of cancer spots, so you know what to look for.
No worries about the photos, I can't place them at all so you're doing a lot better in that part!