It had done this before and some judicious cleaning had helped, but there was no obvious crap to be removed this time.
So I have fetched a spare, unsatisfactory keyboard from the basement and have gone to Amazon and ordered this CM Storm Quick Fire XT with Cherry MX Blue Switches which appears to be the best keyboard I am likely to lay hands on for under $100.
It's supposed to arrive on Saturday.
I am looking forward to it. This Targus keyboard is like typing on mush after years of the SIIG keyboard.