How do i go on?

i can't sync with my itunes. it shown that cannot be synced, the device timed out.

before that i can't restore my iphone with my itunes too. and then i can't open my iphone even if i restarted or power off.

So i took it to U-store (like a retailer apple's product at Thailand) and them help me to successfully restore it.

It's alive! but when i'm syncing at my computer, it cannot be sync :'(

i don't know how i go on, help me please

ps* my itunes and iphone are lastest version already

contact me: sanrio.il@hotmail.com

Thank you!