Do lab assistants have to be fully gifted?
Could someone with incomplete gift such as a failed apprentice assist in the lab?
Yes, page 103 second paragraph. It doesn't say "fully" gifted but to presume that non-fully gifted folks can help sounds like special pleading to me. (there is an exception on page 105 dealing with familiars.)
For some reason, my GM has been allowing a failed apprentice to assist in the laboratory... maybe he's doing something wrong, but oh well, I'm not complaining. Personally I think the rules can be flexible on that point, because the only bonus is intelligence plus magic theory, and those are skills that are independent of magical power. I don't really know what an assistant is supposed to do in a magical laboratory, maybe there's a good reason why they need to be able to work magic alongside their leader -- but if they are just there to offer their insight and a helping hand, that should be worth something...
The failed apprentice minor social virtue states that "You may learn magic theory and serve a magus as a laboratory assistant." Ars Magica 5th edition, page 42.
Has this been errated?
It is more that the rules actually seem to conflict. The virtue says one thing however in the help in the labs section it specifically says lab assistants must be gifted.
This sort of creates a potential conflict as to which area of the rules is correct. Is the one an exception to the other?
I don't think it is that difficult. Generally, you need to be Gifted to be a lab assistant.
However, a character with the Failed Apprentice Virtue can also be a lab assistant, as can a familiar. These are exceptions to the general case.
Cool. I am willing to go with that 
Serf's parma, but IIRC anyone that has a magical/faerie supernatural virtue (second sight, shgapeshifter....) is considered to be gifted. Maybe their gift is weak, but they are still "touched". As such they can help in the lab if they learn MT.
Those guys are not common, but far from rare. I think most magi do not have more lab assistant for a secrecy thing, not for a problem of finding suitable lab assistants.
Plan B is that you do need to have the fiull gift, so only other magi will be able to assist you. In that case all the talk about lab assistants is quite a moot point to start with in most sagas since it would be extremely dangerous to have a lab assistant that can be claimed as an apprentice at any moment by an other magus just to annoy you, have his brain read out AND then be expeditiously disposed off once your secrets are uncovered.
Cheers,
Xavi
No, I don't think so. You need to have the Virtue The Gift to be Gifted.
In character, it might not always be clear whether a particular character has The Gift or merely a lot of neat supernatural powers, but that's a different issue.
Remember, your familiar can be used as well.
Depends how you read the rules - and they could go either way.
What it comes down to is... "Is a "flawed Gift" still The Gift?" or is The Gift "all or nothing"? Can't become a mage if your Gift is too badly flawed - but (apparently) those failed apprentices (or "never could be" apprentices) still have The Gift - so where does that leave one? 
YEah, that does beg the interesting question. If their gifts are enough to be lab assistants (but can't be opened to arts), can they still learn supernatural virtues?
And of course, there's the conflict between in-game and out-of-game language.
As far as the rules go, I read them a requiring the Gift virtue. If you don't have that, you can't contribute to the lab total.
But in-game, magi might recognise different levels of "The Gift", from the old woman with The Sight, through an Un-Gifted Learned Magician who has been through a number of initiations, to a failed apprentice with th Flawed Gift.
Exactly.
I was thinking more from the point of view of a potential apprentice - which is how one gets a "failed apprentice". But what ~is~ that, and what then is their status?
(And two things are true - one, The Gift virtue is a 0-point virtue, so any NPC could have it at any time. And two, altho' the Rules do mention "Flawed Gifts", there is no "Flawed Gift" virtue. And I'm not sure there are adequate Flaws to completely "cripple" The Gift to the degree we're talking about; tho' you could have a magically crippled mage, certainly, they would nonetheless and undeniably be a Hermetic mage, if a painfully weak one.)
A mage finds a promising young tyke with "The Gift" - InVi spells show it's there, etc etc. Claiming requires opening the Arts, so... the mage starts to test the young'un in that season. And it becomes clear that it would be "nearly impossible" (or pointless) to open their Arts.*
[i](* "How" this becomes clear is never discussed in the rules. It would be a harsh surprise to a Player Character, but an interesting plot twist never the less. But at some point it seems it does happen, if less often to Player Characters. 
I also want to think it has to be the "Opening of Arts" (or very close?) that is the "point of failure" - if it's the Gauntlet, or ~any~ time after the Arts have been opened, then you have a (limited) sorcerer who has (most?) all their Arts but no Hermetic recognition/membership - and that's a different animal, and a different discussion.)[/i]
So... we have someone with "The Gift" but who is significantly and obviously unpromising for (further) training - so what does one have then? A lab assistant.
In theory, another mage could claim them as an apprentice and try their luck* - but (also in theory) the first Parens would probably not have given up easily. (If the non-apprentice had promise, they would have been sold, or kept secret.)
(* They are no longer an apprentice if they are not actively being trained, but, I ~believe~, would fall under the same area of the Code as any other mundane servant - The Code does not recognize degrees of Apprenticeship, either they are or are not - and this is not.)
There are LOTS of considerations and plot hooks that start jumping out at this point - for PC's who find such a person, for PC's who find an NPC (mage, slave trader, whoever) with such a person, or find such a person on the run from the above.
We have added the Virtue/Flaw "Minor Gift" that is something like that(though possibly a little bit better), as a Virtue it reduces the social penalty, as a flaw it only penalises the magic ability.
And it does so by allowing you to spend one more(just one) Virtue to purchase a few Arts at art progression or twice as many with Ability progression(and never both T and F).
Makes for fairly interesting characters really. Sucks as magi, but still usable as PCs.