Peggy, if the light looked okay with a gamma of 1 it will never be correct with a gamma of 2.2 unless you adjust the intensity.
Basically, especially when using quadratic lights, we have to crank up the light way behind what is actually "physically correct" to get enough light with a gamma of 1. So, as soon as you correct to 2.2 everything get lighter.

My suggestions:

• If you have procedural materials in your scene, make sure you add a gamma correction node with a value of 2.2 before the diffuse output (be careful with barks materials, they often have a combination of texture maps and procedural: if so you must click on the little gamma symbol near the texture map and choose gamma = 1. Then, you must add a gamma node of 2.2 before the output).
• You might need to adjust the sky color too (atmospheres were created to work with a gamma of 1 and it doesn't look like they update automatically to work with a gamma of 2.2.
• Finally, you might need to tone down all the artificial lights used in your scene.

I hope it will help you. The introduction of a linear work-flow in vue is a really great thing in my opinion, but the downside is, we now work with "legacy" presets and, with the exception of those using texture maps only, they all need to be updated to match the more physically accurate gamma of 2.2 now used.

Also, ddaydreams, is right, beware of the natural film response checkbox. It really tends to wash out renders (in fact, you even see that during the calculation phase for a radiosity render where the black part turn to gray