remount error, android 4.3? [solved]

[JJMC]

Edit: It's solved in the beta!
Lucky me

Hi,
Just got my new nexus 7, android 4.3, rooted, root functions everywhere is checked.
When I try to copy to /system or press the R/W button there, I get remount error, always.
When I try that on my phone, android 4.1, it works. It also works with root explorer.
Has this something to do with the new android 4.3 restrictions?

Thanks.