why doesn't my external monitor display its native resolution?

Macbook Pro 2011, 15".

Lion.

Acer AL2032W external monitor.

This monitor has never displayed its native resolution of 1680x1050 and I've found solutions online to force resolutions: SwitchResX in OSX, and Phoenix EDID creator in Win7 (bootcamp). Until now, this solution has worked. Last night I upgraded to Lion, and now SwitchResX will not activate the custom resolution I have created, even though it used to work.

I've tried editing the com.Apple.boot.plist file to include this resolution, but this also has not worked.

Acer says the product is discontinued and no longer supported.

I'm waiting to hear back from the guy at SwitchResX.

Any other solutions? Stretched scaled displays suck.