What WotC means by "fixed range"
Hi Bob,
What they mean when they use the term "fixed range" are spells which are personal spells, but which have a range in the spell description. All of the "Detect X" spells are like this, e.g.
Detect Magic
Divination
Level: Brd 0, Clr 0, Drd 0, Sor/Wiz 0
Components: V, S
Casting Time: 1 standard action
Range: 60 ft.
Area: Cone-shaped emanation
Duration: Concentration, up to 1 min./level (D)
Saving Throw: None
Spell Resistance: No
The spell has a range. That range is fixed, but it is actually a spell that affects the caster only and lets him do something over that range.
Put it this way, if the primary effect of the spell (or enabling of effect) is not personal in range, then Persistent Spell doesn't work on it.