I used a screwdriver to push the clip down, and a second one to bring it around. The big problem with this, of course, is when you miss, you can hose the mobo that way too.
Did it just snap randomly, or did you let up on the clip tension when it wasn't all the way in?
Oh...not that it matters, but I have FOP-32s with the Delta fans added on...but the same clipping mechanism is used.

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