Every time I wake my Macbook it switches applications after wake. How do I fix this?

Whenever I close my MacBook, and then come back after it's been asleep, I'll open it, and it'll make a sound while it's waking the harddrive, which is normal. But then after that it'll switch the whichever application is active with the second-most active on in the tab-switcher. Does anyone know what would cause this?

This Apple Support article overviews a similar issue. This is on a Early 2010 macbook pro, and OP on the linked thread tied the cause to the "require password after 5 minutes" setting in Security and Privacy. OP solved this issue by switching to "require password immediately"

Have you done all updates up to 10.7.5?