I was having trouble rooting or installing CWM after upgrading to VibeUI/VibeROM 1.5 on my Lenovo K910 and after searching the chinese forums it appears that the bootloader becomes locked and there is no way to unlock it or install CWM recovery.
Finally found a method to upgrade to viberom 1.5 while maintaining root and able to install CWM recovery & gapps.
Download this and follow the steps. There is a text file which contains links to stock firmware and vibeui1.5 update as they were too large to include in this package itself.
sorry for the short intro but i hope the package is self explanatory once you unzip/unrar it.