I got a weird problem in Dernholm... I just did the tax collector quest, but King Praetor dislikes me (I tried to charm him after he gave me the mission) ... when I hand over the gold to him, he and his gaurds attack me! Any idea how I could salvage this mission?

A previous save from before you cast the Charm spell; or cast the spell again and then make a run for it.

One of its side effects is a huge drop in reaction once the spell wears off; if it falls to below (IIRC) 10, you'll be attacked on sight. It turns out that people don't really like being mind controlled. Go figure.