Sounds like a corruption of application management rather than anything specific to OpenLog. I've seen this before with various plugins, when it gets confused about whether a specific plugin is installed or not.
Check plugins and features folders under IBM\Notes\Data\workspace\applications\eclipse. Delete anything for com.paulwithers.openLog that's there. It may not have removed both the feature and the plugin.
If there's nothing there, check Help > Support > View Log or View Trace for any messages referring to the plugin.