Start screen not responding

[valiant john]

Start screen on Lumia 520 is not responding sometimes. Even if I click the apps, they are not opening.

 

[Zachary Boddy]

How long have you been on whatever build you're on? If it's more than an hour go ahead and do a hard reset. A hard reset is recommended after installing a technical preview as it does sort out bugs and such. However, I'd also wait an hour right after installing a new build because there's been a migration bug with previous builds and I'm not sure if it's gone in 10166.