We kind of got into a bit of an argument last week on this, but the rules don't seem exactly clear on when a magic user has to manage his power when he goes past his threshold. The rules don't seem to note for example, when exactly do you check to see if the magic user has too much power. If he has too much he has to spend manuevers and such to manage it, so in a turn if a wizard had used his manuever at start of turn already, now the wizard would have to suffer the fatiuge immediatly to pay for a new manuever, or is this only done at the start of a wizards turn?

Timing seemed to get tricky on this as your not supposed to be able to use manuevers during actions and they have to be done before or after your actions, so with quick casting a spell this seems to bring up an issue possibly? Or is it assumed that when a wizard quick casts, that they ignore the rules for having too much power since they are casting a spell immediatly and venting out that power then?

Power is managed in the 'End of Turn' phase.

If the wizard has already spent his free maneuver he needs to spent a stress or face the consequences. As he can channel and cast in the same turn a Bright wizard and build up a lot of power and then dump it into a spell with extra spell damage.

As Fresnel mentioned, it's all clarified on p.7 of the FAQ/Errata:

Wizards: Managing Power
To clarify the fact that wizards naturally gain and lose power over
time, these rules apply to arcane spellcasters.

Equilibrium
During a wizard character’s End of Turn phase, if he currently
has more power than his equilibrium, he must either perform a
manouevre to maintain this extra power, or loses one power. Conversely,
if the wizard is currently below his equilibrium, then he
gains one power during his End of Turn phase. See ToM p. 34 for
more details.

Excess Power
A wizard checks for and resolves excess power, as outlined in ToM
page 34, during his End of Turn Phase.