iTunes problem with syncing

[Oranortarlom16]

I am a new user of an iPad 2 with ios 5.1 using itunes 10.6. At first my iTunes was properly adding songs, etc. But now i am not able to add any songs,videos or apps using it. I now use copytrans manager for transferring songs,videos and apps. But i still face another problem : im only able to use apps which can also be used on iphone, i.e. I cant transfer only iPad compatible apps to my iPad!!

Does anybody know the solution to this??? Is it my iTunes problem or my iPad's ??????? Please HELP!
Thanks in advance to anybody who can help.