I added musics to my ipod 3g from my laptop then afterwards all my downloaded application suddenly freezes.what will i do? Please help me. Thank you in advance :)

I just bought a second hand ipod touch 3rd generation.then i added musics from my laptop to my ipod

Suddenly all my installed application freezes.when i tried to download again from the store,still my ipod

apps freeze including the apps that i just download..what will i do? Ill appreciate any answers..