You might have a bad sata cable.....Alot of the cheaper stock cables are just simple plugs, but the newer high end cables have clips that lock in the plug.
I've had my share of crap connectors before and you're right sometimes the drive is there and other times it won't connect.
JQ
------------------------------Intel C2D E8400 @3.0GHZ, Gigabyte GA-EP45-UD3L motherboard, 4GB OCZ vista platinum DDR2-1066 , Seagate320GBsataII 16MB HDD, BFG GTS250oc 512 GDDR3...3Dvision glasses and samsung 120HZ screen.
Reply to johnnyq1233