You could try hot water, maybe on a gentle cycle. That's probably what I'd try first.

Have also read (after reading your question) that vinegar helps with bleeding colors. Just google: jeans vinegar. Here's the first result.

Here is a link that might be useful: http://jeans.about.com/od/Jeans101/a/How-To-Keep-Your-Jeans-From-Bleeding.htm

Diluted bleach wont ruin them. I've done it successfully.

The trick is to not use too much, make sure it really is diluted and mixed with the wash water before putting in the jeans.

Run the cycle longer with a little bleach (1/4 cup like you said).

You may as a precaution thoroughly wet the jeans before putting them in the bleach/water mix (as to buffer the denim and not have it absorb the bleach/water all at once).

Before the cycle drains, check to see if there is any fading, if not start the cycle at the beginning again.
If you do see some fading, have the cycle continue to the rinse cycle and spin dry. Then line dry.
The bleeding should be diminished.