hi i have a problem with the jailbreak. when im running the program, at the home page there is a window that tells me that: certain operations (like a5 jailbreak) are disabled due to incomplete itunes libraries. please be sure the latest itunes is installed.
then it tells me that it couldn’t load mobile device.dll....I already downloaded the latest Itunes available. Please help me.

I dont have another computer and all of music and pictures are on the one I am using. I never have had this problem before. I wonder if it's because i'm running on IOS 5.1???

I am using iPhone 4 with iOS 5.1

I have the same problem, i 'm trying to do the jailbreak on an iPhone 4 iOS 5.1.
I used Sn0wbreeze to do the preservation baseband option, then i wanted to do the jailbreak with "Redsn0w 10b6, 7 and 8", but all of 'em give me the same problem, i need the "Mobile Device.dll" but don't know how to get it, also, i have the lastest version of iTunes.

I hope to find an answer to this, thx, sinceraly.

you have to download itunes 10.5.3, the problem is caused by the latest version of itunes

Okay i downloaded itunes 10.5.3 like you said now i'm getting this error message from itunes. The file "iTunes Library.itl" cannot be read because it was created by a newer version of iTunes.....UGH I just want my iPhone jailbroken like it used to be it was never this damn hard!!!!!!! Please help!!!

I had this trouble when you open redsn0w right click it and run as administrator, this happens a lot on windows 7.

hi all i might have a solution to redsn0w MobileDevice.dll error,just copy the redsnow exe file and put in to program files/common files/apple/Apple Application Support and run as admin and should work,have tested on win 7.from reaper71.