Permanently afflicted by a "slow" spell...Help?

Hi

I was fighting some spell-casting undead in the sewers of Caladon the other day. During the course of the battle, a liche cast a spell, accompanied by a "clock-ticking" sound effect, which had the effect of considerably reducing by character's speed, as well as the speed of one of my followers.

Now, after weeks of travel and adventure, the spell is STILL affecting me. Is it ever going away, or do I need to do something to get it removed? Is this a bug of some kind? Since I'm playing a fighter-technologist-thief character, who relies on Backstab a lot, this is quite debilitating to my character.

Some help would be much appreciated.