I don't know if running the essential fix can be done by an iPad with 4.3. In fact, I don't know if it's even available to that version ... did you try going to Cydia and see? If it's possible, it should show up automatically. If it doesn't/hasn't - it won't apply to your version...
As far as I know, Comex only "repaired" the CCK issue with the JailbreakMe 3.0 (that's for iOS 4.3.3).
So, your best bet [to get the CCK running properly]
would be to upgrade to 4.3.3. However, that's only possible
if, and only if, you've saved your SHSH blobs for iOS 4.3.3. If you haven't, this discussion is over (cause you can't upgrade the iPad2 to anything but 4.3.4 without 'em).
So, I'll assume you have 4.3.3 SHSH blobs...
My first suggestion would be to ensure you've run a complete backup first, both in iTunes for the App Store stuff and then something like PKGBackup for Cydia tweaks and Settings.
The easiest way to restore/jail break is to (1) restore the iPad2 to iOS 4.3.4 (just select restore in iTunes, follow the directions ... wait ... then select "restore from backup") and then (2) follow the steps here:
http://www.ipadforums.net/jailbreak...815-how-downgrade-your-ipad-ios-firmware.html
(3) Once you are on iOS 4.3.3, go to JailbreakMe.com (via the iPad's stock Safari app) and press the free button ... press the install button ... watch Cydia load. Done!
Hope that helps - let us know how you get on.
Marilyn