Mac mini hangs on restart

I have a Mac mini (Mid 2011) that sometimes hangs on restart. Specifically, after selecting RESTART from the menu command the restart process begins. A dialog box is presented for choosing to reopen existing windows and applications. The checkbox in the dialog is selected by default.

If I leave the checkbox checked my machine usually restarts as expected. When I uncheck the box my machine usually hangs at the gray screen with the rotating "gear" animation. I've tried to wait it out but after 15-20 minutes I figure I can safely assume something is wrong.

I've performed an OS X restore, twice. I seem to remember installing a firmware update recently also. I'm definitely running the latest version of the OS. I've cleaned caches, zapped the PRAM, disconnected all external drives and peripherals, but nothing I've tried so far reliably alieviates the problem.

I'm wondering if anyone else has noticed this, or a similar problem.