Windows File Sharing sometimes gets into a bad state and needs re-installing. Use the following steps to uninstall and re-install it.
If you still get a timeout error after the steps above, try rebooting your iPad or iPhone. If you still get the same timeout error message, do you have another computer on your local LAN that could be used to test the connection to this Windows 7 machine? If so, a UNC path such as "\\Win7Machine\ShareName" in Windows or "smb://Win7Machine/ShareName" from Mac Finder's "Go->Connect to Server" menu will attempt to connect using the SMB protocol. If these cannot connect, something must be blocking the network packets on your Windows 7 machine.