Follow Thad's link to the other discussion and use Brandon's fix from there (installing last version of Chrome side-by-side with the latest). All other approaches were met with failure for me and although Firefox is much faster and more stable, I just can't stomach developing on that browser anymore except during cross-browser test waves prior to checkin. I imagine the GWT team will get the plugin fixed in the next few days and the old version of Chrome in question is only about 4 weeks old so not a big deal.
Also, so you don't spend time figuring it out you are looking for chrome v21.0.1180.89. That was the version prior to v22.0.1229.79 that was released yesterday that broke dev mode.