The type of lock that's acceptable may be predetermined by your system administrator.
Where I can define what's acceptable? I can regenerate the certificate if needed.
So I can use slide lockscreen again.
(I'm using CM9 RC1, Android 4.0.4)
The problem with disabling the lockscreen security using the toggle/profile is that the lockscreen widgets don't appear either so you can't slide to unlock. Also, when you reboot your phone the buttons don't work until you retoggle the setting again.
Another way is to install the certificate as usual then backup the /data/misc/keychain and keystore directories using something that preserves the ACLs such as Root Explorer to a location that supports ACLs. I suggest copying them to /tmp. Then clear the credentials from Settings and enable Slide To Unlock. Then copy back the folders from /tmp. The CA will be installed.