I'm sorry to "revive" the topic, but it describes the problem I just had and I see that there was no answer to it.
I had the same problem as Cloudy: did all the quests, starting with the giant rats one, told about it to Z and to Peltar, then I finished all the other quests. I told Peltar to send us back to trigger the second part of the quests, then I went to the thieves den and killed the thieves, went back to Z to expose him but talking to him I had only the "nothing right now" answer.
Talking to Falco did not comprehend the Z option. Since I didn't talk to the people at all prior to do all the quests, I talk around a bit and get the journal entry about the girl who's been bitten by a rat. From that moment, talking to Z showed both the "nothing right now" and the "we haven't gotten to the rats yet". Checked the global variables, BHGuardQuest was 1 - but since I already told both Peltar and Z that I took care of the rats, it must've been 3 (I saw the two floating texts about the trap door and the rats in the guard compound) that time, and something reverted it back to 1. I bet it's the journal entry about the girl.
I set it to 3 again, but again no Z spy quest even if I already told him all the rumors we collected (but I told him AFTER having asked Peltar to send us back). I set the BHSpyQuest to 1, and now Falco gives me the option to talk about Z.
EDIT:
Before setting BHSpyQuest to 1 I checked it, and it didn't exist.
/EDIT
I bet it's an order issue (if you have already done the GuardQuest, then pick the rumor about the girl, BHGuardQuest reverts to 1 - probably same thing for the Spy quest, one have to tell to Z the rumors before talking to Peltar, and possibly do the quests after having collected all the possible rumors, as I did in my previous run, in which I had not these problems).
Edited by kthxbye, 08 March 2009 - 06:25 AM.