I've got an iPad 2 32gig and I can't update it to the lastest iOS 5.1. I've tried updating my iPad by connecting it to iTunes and I've also tried updating it directly on my iPad through the settings tab but I get similar error messages

My iTunes account knows that there is an update avaliable for my iPad but when it goes to retreive it I get the error that "the network connection cannt be established".. But I'm connected online and I can access my iTunes account. I've done all the troubleshooting on the help pages and nothing!

So I decided to connect from my iPad and update through the settings tab and I get the error "Unable to checkk for update". I've reset my network connections on my iPad and still nothing

What am I doing wrong?