Sounds like a buggy context menu hook. If it started right after a USB drive was inserted then it's likely that either the drive came preloaded with "value add" crapware (I'm looking at you, SanDisk) or that the USB drive was infected with a piece of autorun malware that hooks the context menu in Explorer.
Look through the registered shell extensions with ShellExView and look through the shell menu handlers with ShellMenuView for suspicious entries. Don't go disabling things willy-nilly, but going through the (admittedly long) list of items may yield some answers. Anything from Microsoft is safe and may be very important, you're looking for entries which don't name a Publisher or that was modified near the time the problem started is immediately suspect.
If it is malware then you can run some diagnostics and post the logs at various analysis and removal forums like Bleeping Computer, Malwarebytes or 247fixes for a volunteer to look at and advise removal steps.