When sampling music on iTunes, it just clocks and never starts the sample.

This is on my Windows 7 laptop. I can play music from my library but when I try to sample music (any music) iTunes just clocks. I've uninstalled, reinstalled - same issue. Disable firewall/antivirus - same issue. It was fine a week ago, haven't done any upgrades or installs (other than iTunes) but the problem persists. I've let the sample clock and clock for 20 minutes thinking there was some sort of lag in the iTunes store, but nothing happens.