Sometimes I find my pc wants to play "spin-outs" as I call it personally. I don't know if you had tried to close everything down on your pc & turn it off, then leave it for a few minutes & turn your pc back on... nice & fresh.... lol. Sometimes I think these machines have hormone problems at times & just want to mess with us by getting things mixed up in it's insides.
Most of the time I have found it to work, the other thing is it maybe running slow if it hasn't had a "cookies" (History) clean-up.
Good luck,
Reggie

Usually when that happens it's just a glitch in your own system. Who knows. Reboot and try again. If it keeps happening then you need to run your disc dr software. Probably it's just a little tic in the system and will be gone when you restart. Hope it's that easy!