After Effects CS4 audio levels expression problem

Question

Basically what I have is a layer with a checkbox. There is also an audio layer which has its audio levels linked to the checkbox by this expression:
if(thisComp.layer("White Solid 1").effect("Checkbox Control")("Checkbox")==true)
[5,5]
else
[-20,-20]
No matter if the checkbox is checked or not, when previewing the audio is played as if it had Audio Levels set to 0. When there is no expression, the audio levels can be controlled normally. But when the expression is applied, the Audio Levels is stuck at 0dB. This problem seem to be apparent only when previewing. After the audio is rendered, the file plays as it would be expected. Could anyone please help me with this?
EDIT: Also, the waveform seems to react normally to the checkbox.

Answer 1

Thank you for the reply!
I never put the curly brackets when there is only one number since it saves some typing. I tried this time, but it made no difference. Also tried writing 1 instead of "true", still the same problem. I also tried this expression:
temp = -40 + 40* comp("Main Comp").layer("SOUND CONTROLS").effect("Appearance Sounds")("Checkbox");
[temp, temp]
The same problem persists. The preview sounds wrong, the render sounds right.