Good news -- Looks like you're 1/2 way there.

Check the voltage on one of the data lines.
When you slowly turn the encoder wheel, does the voltage vary between high and low?
If it does (and you have a second multimeter), when you slowly turn the encoder wheel, do the two data lines alternate changing states between high and low? (phase 1 to phase 2 B changes, 2 to 3 A changes, 3 to 4 B changes, 4 to 1 A changes )
Coding for clockwise rotation
Phase A B
1 0 0
2 0 1
3 1 1
4 1 0
Coding for counter-clockwise rotation
Phase A B
1 1 0
2 1 1
3 0 1
4 0 0
The only other thing that comes to mind is whether the boards you are using are "
active low" (most common configuration) or "active high".

Scott