weird problem : whenever I copy songs from my computer to my iphone it misses the first 30 seconds?
ZoneAlarm, and other firewalls, may occasionally interfere with the syncing process.  Turn off the firewall during sync to see if it's the problem.  If it syncs well after that, contact your firewall provider and ask for the proper setting so you don't have to disable it every time you want to sync.

Also, iOS 5.x can sync wirelessly, which may resolve the problem.