error 1600 and 21

[harold1]

Keep getting itunes error 1600 when trying to upgrade with pwn DFU and error 21 when trying to upgrade with restore mode. Can not figure how can I upgrade to 5.01 from 5.0. Any ideas? I
Tried 2 computers, no luck.

I have the same problem as the dude above except mine os occurring when trying to upgrade ios4.1 to 5.01. anyone have any ideas?

 

[Sly3GS]

Using my wires MacBook helped

Hi Harold1,

I seem to have had a similar problem.
When trying to upgrade from a iPhone 3GS 4.3.3 to iOS5 (I had installed Cydia months ago, never used it and I felt it did not work properly (lost app icons, progress indicator everywhere)) and thus wanted to completely wipe and upgrade it.
When trying from my own Mac, I run into the vicious "Error 21 -> maintenance mode" cycle which forced several reboots and always ended up again in maintenance mode. I saw my iPhone already in iPhone heaven.

On my Mac also TinyUmbrella is installed, so maybe some hostlists have been altered which may cause this issue.

After several fruitless attempts I simply connected the 3GS to my wife's MacBook and there iOS 5 was downloaded and installed without any problems. I now kept it as "new" iPhone but re-established the link to my iTunes library.
So far everything fine. I guess TinyUmbrella and Cydia somehow cause issues.

Best regards,
Sly

 

[Crystal-RX]

Follow instruction on this thread;

https://forums.macrumors.com/threads/1300041/

 

[porsche928]

Hosts file!!!

THanks Guys, basically I pulled the hair outta my head for a good few hours into the night ... till I saw the above post and recalled that I had once in a previous life jailbroken my iPhone3 and set my hosts file up. Once I commented out the old Cydia server in the file, I was able to restore in iTunes ... (was getting both 21 and 1600 errors btw) CHEERS!!!!