I am replacing some old can lights with some new ones - the two cans aer on a three way switch and the wire from the switch to the old cans was a 12-3 - the way the cans were wired had the red wire twisted together while the white and black wires fed the lights - after the second canister light there was another wire (12-2) which looked like it feed back to the panel. When I wired the lights with the red wires being the runner and then tieing the 2 wire in with the white and black I wasn't able to turn the light off - what is up

Roswell : no wonder the lights behave strange ! :D
.
Basic color coding for electrical wiring :
.
Green=ground
White=neutral
Red=phase (hot)
Black=switched hot
.
"3" wire wiring contains hot + neutral + switched hot (+ opt. ground)
Hot wire is used to feed one side of all wall sockets and/or one side of the light switch.
Neutral is used to feed other side of all wall sockets and lights.

"2" wire wiring contains neutral + switched hot (+ opt. ground)
Switched hot wire comes from light switch and goes to one side of lights.
.
You must have connected the red (hot) wire to the black (switched) wire somewhere. Therefore the switch is actually bypassed, and the lights remain "on".
.
Rewire as follows :
.
Red (hot) goes to the switch. The switched wire is black.
This black together with the common-to-all neutral (white) should feed all lights.
.
Success!
As always : if you require more info, please let me know. If this solves your problem, please rate the answer provided! Feed back is always appreciated!
;)


The lights were wired to white and black

Is this what you are trying to do?

Good drawing by HK, in case its not clear, black and white between switches are the travellers and only connect to both switches, The switch on the left is the "switched end" which is the end that goes to the lights(hot).
The Right switch is the "Hot end"(the 3 way that has the constant hot(black)and goes to center common terminal.