irdeggman said:Found it - and it renders my notes moot.
Complete Arcane pg 71
"The only differences between invocations and other spell-like abilities is that invocations require somatic gestures and are therefore subject to arcane spell failure.”
Mind you, the eldritch blast is listed seperately, and doesn't seem to have the restriction that invocations do, as far as I can see. So a grappled warlock can still blast his enemy if he makes the Concentration check.