Loses wifi when lid closed until restarted
I did a post on this about a month ago but since then I've found out more about the problem.
Sometimes when I shut the lid on my macbook it can no longer see any wifi networks when I open it again. It doesn't happen every time but fairly often and the only way I have found to make it see wifi networks again is to restart it. I know it only happens when I shut the lid because I tried leaving it open for over a week, sleeping it from the apple menu and I didn't get a problem the whole time.
I've reset the PRAM and SMC and I've even tried running the laptop off an external hard drive with a clean osx install on it but no luck.
If anyone can help me with this it would be appreciated as I'm hoping to use the macbook for school, where I will be constantly opening and closing it all day. If I have to, I'll buy an external wifi adapter but I'd rather have it working properly.