changing lightswitches

I have removed a light switch from my den, and am having problems installing the new switches. The original switch was a 2-in-1 switch. It had 2 black wires going to each switch, while the other 2 were connected to a single screw on the opposite side of the other black wires. Neither the 4 white wires nor the 4 ground wires were connected to the original switch: all the whites were connected together, and all of the ground were connected together - still are. I am trying to replace this switch with 2 separate switches, both of which have 2 connector screws on the right side and a ground connector screw on the left side. I was able to connect all of the blacks to the right side connector screws, but only got one of the lights working. This is pretty complex for a person used to just swapping out like switches. Help!

Grant

If its not too late to help you.
Take the two wires that were under one screw on the original duplex switch and tie them together along with a wire nut and two more black wires about 6 inches long which we will call pigtails.
Now connect one pigtail to each new switch screw. Then connect one each of the black wires that were on the other side of the old duplex switch to each new switch.

The problem started when you failed to notice the tie strap on the old switch on the fed side of the duplex switch.

Larry