I had this issue and others like this with some of the LGNPC mods and got some feedback from Cyrano, their editor.
Some of the Bethesda quest dialogue entries are badly filtered, so it's possible that you can end up doing parts of quests that are intended for another faction. Basically, if both you and the NPC "know" the same topic, then it's available to talk about and they will end up leading you down the quest path. The bug is, you shouldn't "know" the particular topic unless you've been spoon-fed to that location by being the correct faction member and doing previous quests in the series, but the Bethesda devs (or LGNPC ones) screwed up and forgot that you can learn the topic another way. So you end up in the middle of a quest you shouldn't be on and hit a brick wall at the end because a part of it (like returning the Morvayn Ash Statue to Lloros Sarano) IS correctly filtered. In this case he refuses to take it from you because you're not in House Redoran, so you can't be on the quest...
There are a number of ways to deal with this. For official quests it's as simple as finding the correct journal entry on http://www.uesp.net/wiki/Morrowind:Mission_to_Morvayn_Manor and manually closing them off that way through the Console. In this instance, you get to keep the Morvayn Ash Statue that Lloros Sarano won't take, but the quest closes. The problem is that then opens another door to another bug... because "fixing" these bugged faction quests so that you can complete them in some meaningful way when you stumble into the middle of them (as an opposing faction member) and get "official" quest journal entries is not trivial. Dialogue entries you might get in the conclusion are designed specifically to lead onto the next faction quest in the series... so without susbstantial rewriting you'll end up being assigned more quests you shouldn't and that you can't complete...
Cyrano's feeling is that faction quests should be strictly enforced as only being done by the faction, so that you never end up in this situation. For instance, we just had a discussion over Delyna Mandas - I believe he's implemented a fix somewhere in LGNPC that will actually disable her in Tel Fyr if you are not House Redoran so that it's impossible to rescue her, since that's strictly a House Redoran quest (given by her grandfather in Ebonheart). My view is that her being there should be totally independent of your faction and you should be able to rescue her if you wish (do the "good deed") and maybe get a reward of some sort even if it wasn't your official quest. That seems more in keeping with the do-anything-anytime-anywhere spirit of Morrowind. This is implemented in other quests fairly well, such as avenging Ralen Hlaalo for House Hlaalu (by doing the Larrius Varro Council Club quest) even if you're not a member of House Hlaalu... so IMHO ideally the bugfix should be to improve the opportunities for players to do and complete quests, not restrict them by artificially altering the world dependng on what faction you are...
Sadly, given the current stalled state of the Morrowind Patch Project and (quite apart from his personal inclination not to fix it) Cyrano's understandable focus on fixing and improving LGNPC rather than debugging vanilla Morrowind, this isn't going to happen any time soon unless some other person/group looks at all these scripting errors in detail.