The quick release on my shimano sora brakes pops open during braking Occasionally, when using my bike with shimano sora brakes on the front and rear, the quick release will pop open during braking, reducing my braking power.  Is there some way to prevent this?  Is it likely that I have something adjusted improperly?  Do I just need to buy more durable brakes?

As a note: I am using these brakes on the bike I use for bike polo, so often times, I am jamming the brakes very hard to stop quickly after a sprint.
On Sora brakes, if adjusted correctly, it should not be possible to force open the wheel release lever by applying the brakes. 

Likely, your brakes are adjusted too tight to allow the lever to close completely. Try releasing a few millimeters of cable, and see if the problem continues. 

If it does, you may have a damaged or defective brake. Take it to your LBS, and have it checked out.