I had to create this post because for the past week and countless hours of trying to upgrade to 5.0.1 I get getting all sorts of errors, if it exist I got them. I also, edited the HOSTS file to every which way posible. I had ios 4.3.1 trying to upgrade to 5.0.1 with preserve baseband. This is what I did to get it to work.
1. Download the latest version of RedSn0w
2. launch redsn0w and click on extra.
3. Create a custom IPSW with preserve Baseband.
4. Connect your phone and save the SHSHblobs.
5. With RedSn0w opend click on more and select Stitch IPSW. (it allows IPSW with preserved Baseband.
6. select your preserved BB IPSW and stick it with your blobs that you saved.
7. download the latest version of Tiny Umbrella.
8. go to advance and uncheck set host to cydia on exit
9. check request shsh from cydia.
10. start the TSS server.
11. put your phone in DFU mode
12. open itunes and hold shift+click on restore.
13. select the Stitched IPSW that you created earlier.
if you get an error, unplug the phone from the 30pin dock side not from the PC and connect again, try again.
Also, make sure that your HOST file is pointing to Cydia.
GOOD LUCK!
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# Copyright (c) 1993-2006 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host
# localhost name resolution is handle within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost
74.208.10.249 gs.apple.com
1. Download the latest version of RedSn0w
2. launch redsn0w and click on extra.
3. Create a custom IPSW with preserve Baseband.
4. Connect your phone and save the SHSHblobs.
5. With RedSn0w opend click on more and select Stitch IPSW. (it allows IPSW with preserved Baseband.
6. select your preserved BB IPSW and stick it with your blobs that you saved.
7. download the latest version of Tiny Umbrella.
8. go to advance and uncheck set host to cydia on exit
9. check request shsh from cydia.
10. start the TSS server.
11. put your phone in DFU mode
12. open itunes and hold shift+click on restore.
13. select the Stitched IPSW that you created earlier.
if you get an error, unplug the phone from the 30pin dock side not from the PC and connect again, try again.
Also, make sure that your HOST file is pointing to Cydia.
GOOD LUCK!
----------
# Copyright (c) 1993-2006 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host
# localhost name resolution is handle within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost
74.208.10.249 gs.apple.com