I'd also check my trunk seal...my lid did that after I replaced mine and put it in wrong.
PS: Ahhh, I totally spaced...was obviously thinking trunk all the way. Never mind then...and yeah, I would side with the catching mechanism opinion. Sometimes it happens to my hood, then I just open it and make sure to drop it straight (I am SUCH a mechanic!!) and that seems to take care of it.
I have the same problem. Generally, you do not have to adjust the cable. The catch mechanism has a metal plate which is pulled back by a spring when the opening cable is released. When dirt or corrosion gets between this plate and the static metal mount of the catch, it binds and does not return all the way causing the problem of the hood popping up. Spraying some kind of cleaner into the area and working the plate back and forth should free it up. You can see this plate when looking at the catch mechanism below the cross beam.
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