I use Windows 7 and my file server is ubuntu. When I copy a lot of files from Windows to Ubuntu the network connection drops randomly and file copy fails. I already unchecked IPv6 protocol and it didn't help.
Is there any other thing I can check?
I would guess you are using wireless, if you are then you're basically using a lot of bandwidth which is probably not enough for you to transfer your files. If it's a g router then it won't have the best streaming capabilities. If you have your heart set on wireless I would go for a Wireless N router (you will need N adapters as well) with a fast connection.
The best bet is an Ethernet cable right into the router, or home plugs are a great wireless alternative.