Computer restarts whenever I close the lid

So I set my power settings to go to sleep upon closing the lid of my laptop, but for some reason over the past few weeks it has decided to randomly restart the computer instead of just going to sleep. This doesn't happen all the time, but with relative frequency. Another problem with it is that every time it does this (meaning everytime it chooses to restart upon closing the lid, not every time I restart otherwise) is that it clears all of my cookies, as well. Anyone have any ideas?

Try updating your BIOS and as many drivers as you can think of: audio driver, NIC driver, video driver, anti-virus...

Almost everything that goes wrong during power state transitions (running->sleep, sleep->running) comes down to a driver bug - or the BIOS

I updated my BIOS and all of the drivers that I could think of, and it still happens. In fact, I think it's almost getting worse; before, it would retain some of my cookies, and now it not only wipes all of my cookies but some of my system settings, too!

The "reboot" might actually be a crash - a blue screen.

If you look in \windows\minidump, you may see a bunch of DMP files whose timestamps correspond to the crashes. They're summaries of the memory state at the time of each crash. If you zip up a few of the latest ones and upload them here, someone may be able to help you work out what's happening.

=/

The minidump folder is empty. Any other ideas?

That doesn't necessarily rule out the crash theory. Perhaps it's unable to generate a minidump because:

(a) There's no pagefile on the boot partition (the one on which \Windows resides). In order to generate dumps, there must be a partition at least ~500MB in size.

(b) It's not actually configured to generate a dump. You can check this in Control Panel, System applet, Advanced tab, settings for "startup and recovery"... set the dump type to "small memory dump".

Also, I'd suggest looking in the event viewer (run EVENTVWR) for any error or warning events with timestamps in the seconds prior or just after the reboot. Is anything being logged?