I had this problem when restoring my apps after the Firmware Update.

I was streaming music from the web at the same time as restoring my apps, as I walked away from the wireless access point the streaming music stopped and the app being installed at the time stopped half way through. I gave it 10 mins with no change; so I cancelled the install; moved nearer the access point and tried again - all was OK.

So check:
How near to your access point you are.
Are there other access points in your area on the same channel.
Does you access point have any problems with it's radio.

Hope this helps