I am fairly new to QGIS, but I had successfully installed QGIS 2.12 on Windows 10 with several plugins, and it worked OK. I wanted to try the Boundless OpenGeo Explorer plugin for QGIS but there was an error on installation. I had had a previous error trying to update the Processing plugin, so I decided to uninstall QGIS, and reinstall a clean version (2.8) from Boundless, as this would have the OpenGeo Explorer plugin pre-installed.
The installation seemed to go OK, but now QGIS will not start properly. It reports something like
Couldn't load plugin XXX due to an error when calling its classfactory() method
for several plugins (
MetaSearch Catalogue Client,
qgis2web etc). Then I get
Couldn't load plugin 'opengeo' from ...",
and the same for plugin
On startups I do get to the QGIS screen, and from the plugins option I notice that there are two entries for the Boundless plugin repository. I cannot delete either of them. And it seems to have carried over the non-core plugins I installed before into what was supposed to be a clean installation. Several of the plugins are said to be invalid.