Easiest use CF root. Look here: http://forum.xda-developers.com/showthread.php?t=1103399

and follow the steps.

But what you have done is correct, insecure, root, then stock kernel. Easier still use what I said above, just takes 1 minute and one click

There are a few ways to root your galaxy s2,but the most simple and widely used method is the cf root method

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Added on November 11, 2011, 2:00 pm
My cpu profiles are:
1200-200 ondemand governor
No uv

pretty simple stuff do note that all of our devices react differently to the same uv settings, some maybe able to uv like hell and no issues,while some may uv slightly then random reboots(me). so try every uv settings to see which suits ur device best

if he wan big big screen, SGSII.

if he wan a strong n long lasting phone, N9's build is somehow better than SGSII.

if he wan unique, go for N9. now whole street oso SGSII, i oso sien d     

Try clearing your caches and resetting the phone through recovery. If cannot then reflash again.

Wait, is that even possible without being rooted?

To make things easy for you, just flash the WIPE version which will delete all your data and wipe cache.
You can also do it manually.