On Npp application startup, a "Unknown exception" popup is displayed. Npp seems to behave normally after closing the dialog.
I was previously running v6.3.2 in both Windows 7 Pro and Windows 8.1 environments. Both environments ran fine. I recently upgraded to v6.5.5 and now my Win7 environment pops the "Unknown exception" dialog, while my Win8 environment runs fine.
I uninstalled all instances of Npp on my Win7 machine and then re-installed the v6.5.5 version, and the condition persists.