Do you have the FullForce or RetinaPad (either or both) tweaks installed on your iPad? Did you ever have them both installed, although you may not have either, or just one, now? Another member had them both installed and discovered that they don't work well together on the iPad.
He had to restore the iPad with stock firmware and then re-jailbreak. He then put only one of those tweaks back on. As I said, evidently, they don't work well together.
So, if you have that problem, I'm afraid your only fix is to restore to stock iOS 5.1.1 and then re-jail break.
If its not those two tweaks, holler back and we'll take another shot at it. Good luck.
P.S. Since you are talking about a jail broken iPad, I've taken the liberty of moving this post over to the Hacking section. Thanks for your understanding.
Thank you so much for your quick reply,
Btw, i never installed fullforce tweak but i did install retinapad.
Yesterday i removed retinapad, and the virtual keyboard is still messing.
The messing virtual keyboard only happens to iphone application which is installed on my ipad2.
Hmm, too much time to re-restore and Jailbreak. Is there any else solution?
Unfortunately, no. If you want the keyboard to display correctly, you are going to have to restore and re-jailbreak. Then, don't re-install either tweak.
Sorry, but thats the only way. And, you might want to go ahead and take the time to do it now, while Apple is still signing iOS 5.1.1. Because once that iOS is no longer signed, restore to that iOS, if possible, will be a lot more hassle than now.