Just to resurrect this old thread, I’ve just updated to an SSD in my late2009 21 1/2” imac, (yes, it was still running the original HDD!).
I have fat fingers and it took me ages to get it to run again. Anyway, I had exactly the same issue with the vertical sync cable. Bent wires which I managed to straighten again and hey presto!
I can actually dismantle the thing with my eyes shut now. :-)