First, my English is not very good, this article may has lots of grammar mistakes.
Hope you can understand what I want to express.
I am the author of 5-Row Keyboard iOS4, 5-Row Keyboard for iPad, 5-Row Keyboard Deutsch and Keyboard Cache Cleaner.
However, in iOS 4.3.x, all these tools cannot work anymore.
In fact, I don't know why they cannot work since I released Keyboard Fixer iOS 4.3+.
Anyway, you can download Keyboard Fixer iOS 4.3+ in Bigboss' source from Cydia to solve this issue.
However, this tweak is based on Mobile Substrate, which cannot run in iFile.
iFile uses root permission (4777) , so only some famous Mobile Substrate addons (eg: Activator, SBSettings) can run in it.
I will try to fix this issue in iFile in the future, however I cannot promise since I'm not a programmer of Object C and iOS.
By the way, the Keyboard Fixer iOS 4.3+ uses some part of the source code from "showcase".
So I made it conflicts with showcase. If you want to install Keyboard Fixer iOS 4.3+, the showcase plugin will be removed automatically.