I’ve just uploaded a new version of WP-Cumulus. Version 1.03 attemps to fix compatibility issues, adds a widget, speed control and several other little things. See here for the changelog.
With the help of Mujahid (and several others), I’ve been able to track down the cause of the “it kills my blog” error. I turns out I was closing PHP’s output buffer once too often, which PHP version 5.2 and newer does not like very much. All should be well for these users with version 1.04. Can’t tell you how relieved I am.