Can you get pregnant while having your tubes clamped?

Yes but <1% I assume you mean after, not "while". Tubal sterilization is not infallible so we quote less than 1% failure rate eg getting pregnant despite procedure. Rate of "failiure" depends upon several different factors. Check out http://www.Cnn.Com/2008/health/expert.Q.A/12/22/pregnancy.After.Ligation.Shu/index.Html for more info.
NO IF TUBES CLAMPED. If your tubes are clamped you can not get pregnant as egg can not reach the uterus for fertilisation.That is if tubes are clamped properly.