I had a similar problem. I would put my MacBook Pro to sleep by closing the lid or manually by using the keyboard shortcut (option+command+eject), and at least one out of every ten times I would open the lid, the computer would not wake. I tried a number of possile solutions posted on user groups including resetting the System Management Controller (SMC). I noticed a few people said that the problem may have something to do with how the wireless card interacts with other parts of the computer. That led me to the first solution.
Solution 1: Before putting my computer to sleep, I turned the airport off. Every time I did this and opened the lid to wake my computer up, my Macbook would wake without any problems.
But this solution is a little clunky (Having to turn your airport off every time you put your computer to sleep, then having to turn it back on upon waking). Then a rep at Apple Tech Support had me do the following. Since applying this solution, my Macbook has woken from sleep without any problems.
Solution 2: Shut the computer down. Turn the computer on in Safe Mode by pressing the power button and immediately hold down the shift key until a progress bar appears in the lower middle area of the screen. When prompted, enter your password to log on in Safe Mode. Go to the apple symbol in the upper left hand corner of the screen -> select system preferences -> select energy saver. Then under the settings for "Power Adapter" uncheck the box "Wake for network access." Restart your computer normally and make sure that the box is still unchecked.
It's been almost 24 hours now and the problem has not recurred. If this does solution does not work on your Mac, there are several other possible solutions at this link (http://www.maclife.com/article/howtos/how_fix_mac_won%E2%80%99t_wake). From reports on other message boards, it sounds like a number of problems can cause this issue including problems with hardware. But if your computer's problem is caused by an interface problem with the wireless card, this may be a solution worth trying.