Error 29 when trying to restore to iOS4

All that the video does, is stop the Restore Loop. It does not however fix the error 29, nor does it fix the spontaneous reboots in iOS4. Also this 3GS was not updated at the baseband during update to iOS4, very odd. I really hope 4.0.1 (due to be released this week, because of iPhone 4 antenna issues) will fix these **** bugs.

here is what i did to get out of the error 29 on 3gs.. use irecovery -s and you will get the gasgauge errors, but do an exit and launch irecovery again and again until you find a prompt with no gasgauge errors.

Then you do the setenv and saveenv commands. That got me out of recovery and made my iphone work, only thing is it randomly reboots...

@gradyboy:

iRecovery did not fix your Error 29, it merely helped you to get out of the Restore Mode Loop.
Still, when you'll restore you'll get the 29 popping up.

As you say @gradyboy, iRecovery not fix the error but the iphone out of the loop, I'm from Argentina, and to update the 3gs to ios4, get the same results

i have had the error 29 for 2 days and found a fix. Now this is for those who can't get to the screen to make a emergency call. this is for those who have a 3gs new or old boot rom. I'm on a pc windows vista not to savvy with the mac. ok, here goes: you do a restore wether by shift + restore or just plain old restore, it'll go about 3 1/4 of the way and throw that filthy error 29. now you start Ireb for windows and hit get out of recovery loop and you will see that it will finish the restore. Then you do whatever it is you want from their. Look this work for me i spent 2 days trying everything you guys mentioned also but none of that worked. this did so i'm passing it on.

It is the battery. I replaced the battery not too long ago. Luckly I saved the old battery. I had error 29 and could use irecovery to exit the loop, then the update would finish but ios4 would reboot every few minutes. I could downgrade back to 3.1.3 and the same thing would happen except 3.1.3 would run stable. I put back in the old battery and ios4 loaded without any errors just like it should, and its running stable. I put the new battery back in and ios4 starts rebooting again. It is definatly the battery. I did buy a larger capacity battery. I would suspect using a replcaement OEM battery would work.

I've gotten over this issue. I dont know exactly what did it. but I'll share all that i did.

3gs 16GB on 3.1.3. jailbroken with spirit.
tried updating to 4.0.1 and got the dreaded error 29. kept repeating same cycle.
used irecover and phone came to life. but kept restarting on its own.
downgraded back to 3.1.3 with shsh from cydia. still came up with the error 29 and used irecover again. which kinda fixed the issues but was back in 3.1.3.
then called apple tech support who said it might be a hardware fault and asked me to do a factory restore by holding the home button when plugging in to itunes to confirm the hardware fault.
then i took the sim out and did the factory restore. wallah!!! the restore worked and now on 4.0.1 and no restarting issues.

Dont know if this would be helpful to any one. but any way. thats how it went
Hope this helps.