Several iPhone 4 users have reported that they are facing iTunes Error 1013 or 1611 while updating their iPhone 4. One Apple Discussions user provided a possible solution for those having these error issues:
For Mac OS X:
Step 1. Go to your “Applications” folder
Step 2. Go to your “Utilities” folder
Step 3. Launch “Terminal”
Step 4. Type “sudo nano /etc/hosts” (without quotes) and hit return
Step 5. Enter your password
Step 6. Use the down arrow key to find the “gs.apple.com” entries. Once the cursor is in front, make sure you comment out the line(s) by entering “#” (no quotes) in front of the text or remove the line that has gs.apple.com entirely
Step 7. Save the file by pressing CONTROL+O on the keyboard
Step 8. Exit the nano editor by pressing CONTROL+X on the keyboard
Step 9. Restore your iDevice
For Windows
Step 1. Start –> Programs –> Accessories
Step 2. Run Notepad or WordPad
Step 3. Click “Open..” from File menu.
Step 4. Browse to Windows/System32/drivers/etc
Step 5. In “files of type:” select all documents
Step 6. Open “hosts”
Step 7. Delete all line that has “gs.apple.com”
Step 8. Hit Save
Step 9. Restore your device