OK I killed The Viciscamera with the potion and every drider I can find, including the drow assassins. But when I talk to Malavon for the reward the only choice I get when speaking to him is "I haven't found anything yet." ARGH! Any ideas? Thanks!

Have you spoken with his sister?
Have you used the potion that you must create in the lab and then used it on the "slimy mouth" in the breeding pen or whatever?

his sister you need to find,
get her your quest will end.

Thank you, I did create the potion and dropped in in the creatures mouth. I also spoke to his sister and convinced her to return. :(

After you finished your business in the cave, were you attacked by more driders at entrance of the cave?

OK dude Bug report!!

If you say you got rid of the drow assassins I take it that you have already cleared the entire cave,sent Malvalons sister back to him and got rid of the 3 new Driders who spawned in the main cave by now.
Remember you have to visit Malvalon thrice: once to tell him that you met his sister, the second time after you get rid of the Viscrema and third to finally meet Ginafae back at her brothers side.
Try activating your pet Flesh Golem and sleeping in the main cave.

If you still dont get the dialogue options, then Sorry Dude: Reload.