You will need to have jailbroken iPhone, iPod touch or iPad to install the unofficial update for MobileSubstrate. You can follow the steps posted here to jailbreak your iPhone, iPod touch or iPad on iOS 4.3 using Sn0wbreeze. Now follow the step by step instructions posted below to fix mobile substrate issues in Cydia after iOS 4.3 jailbreak.
How to Fix Mobile Substrate Issues in Cydia After iOS 4.3 Jailbreak
STEP 1. First you have to launch Cydia, then install iFile and Safari Download Manager for your iPhone, iPod touch or iPad.
STEP 2. Click here via Safari browser on your iPhone, iPod touch, or iPad.
STEP 3. Now you have to download the .deb file to: /var/mobile directory.
STEP 4. Now launch iFile and then go to /var/mobile directory. Then click on the Mobile Substrate .deb file. In order to install it simply click on “Installer” button.
STEP 5. Now you have to restart your iPhone, iPod touch or iPad in jailbroken state.
That’s it. In this way you can fix mobile substrate issues in Cydia after iOS 4.3 jailbreak. If you found any difficulty in following the above steps then feel free to ask in the comment section below. [via]