Q. In Comic 58, Belkar uses a scroll of Cure Serious Wounds, which requires him to have a Wisdom of 14. Since Vaarsuvius cast Owl's Wisdom on him (which boosts your Wisdom by 4), he must have a Wisdom of 10. Why do you have him at less?
A. That comic was trumped by the more recent
Comic 475 in which Belkar admits to having an Ability score penalty to Profession checks. Since Wisdom is the Ability that modified Profession, Belkar cannot have a Wisdom above 9. So we are ignoring Comic 58 as one of those times where "funny trumps rules."
Q. Wait a minute. Cure Serious Wounds is only a third-level spell on the clerical spell list. And since it was Durkon's scroll and Durkon is a cleric, wouldn't that mean Belkar only needed a 13 Wisdom, which means a 9 Wisdom before Vaarsuvius cast Owl's Wisdom?
A. No. Scrolls have no class listed. You use the level of the spell on the caster's spell list. Cure Serious Wounds is a 4th level Ranger spell.
UPDATE: In the wake of another debate about this, two schools of thought have risen, regarding whether a Ranger needs 13 or 14 wisdom to cast the spell. Based on various readings of the rules from the SRD, Wizards.com and Splat Books, it is possible to see different meanings. In the interest of not alienating fellow geeks, the assumption, until explicit confirmation from either Wizards or Rich about which is correct, will be that that funny and plot trumps the rules.