The duration of the entangle power seams to be until you make make your break free roll.
Is the break free roll a standard test ie TN 4 or against the arcane skill roll?
If the Entangle is an Area can you be effected again if you move into the area of effect or is it only those at the time the power was used.
Does the effect come to an end if the caster moves further than Smarts away from the targets?
If the targets keep failing the break free roll are they trapped forever or does the power end at some point?