Plugin Raster->TerrainAnalysis->slope which had initially worked, started showing what another questioner referred to as a "crazy histogram": qgis2 slope analysis from NED data gives crazy histogram
Before finding his question and the answer, I endeavored to uninstall and reinstall the plugin.
I found/still find (QGIS 2.0.1, now upgraded to QGIS 2.4, on Ubuntu 14.04), the plugin "uninstall" button grayed out/disabled.
It's working, but I am worried about having a plugin I installed that does not offer an option to be uninstalled.
Failing anything else--and following my penchant for "trying something"--I would be tempted to use the path information to rename the .so library and see if it disappeared, but better advice or insight would be most appreciated, thank you.