I've had Jaheira the entire time, and have never triggered the quests involving the Harpers...I'm in Ch. 7 now, so I guess its too late, but for the next time through, how do I trigger it?

You actually probably had it and inadvertantly scrubbed it. It starts during a travel sequence, you will be waylaid by a group of enemies who will be in the process of attacking a character laying on the ground. This character needs you to rescue him and take him to the Harper Stronghold. If you cast "Stinking Cloud or Cloudkill" on the bad guys, or had Aerie or someone drop a "Fireball" or some other area of effect spell, you inadvertantly killed the guy you needed to rescue. Ergo, the Harper quest is lost.

I also had a problem with the harper quest..

possible spoilers






i rescued the guy, done the missions to gain their trust, done the xzar montaron thing...then nothing...

first time around jahiera got her summons, i killed the harpers when they turned on me, had a few fights with other harpers then jahiera renounced her status....this time i've had jack shit...

question is, am i screwed