Sierra - 'There is a problem...' when connecting to Windows Vista PC
I am guessing here but it just MIGHT be something to do with the shared printer on your Vista machine. I would be sorely tempted to remove the printer, uninstall the driver, use the printer utility to REALLY remove the driver, reboot and re-add the printer and the printer share.

Windows printer sharing can be flakey, ESPECIALLY if you are sharing it to a Mac. Not sure whether to blame it on the Mac or the PC, but I am leaning towards blaming the PC...