[KDE] Locking the desktop ends with black screen

[Guest]

Hello.

I'm new here and not sure if this is actually a problem of KDE.
Ive installed Kubuntu yesterday on my laptop, downgraded from 15.04 to 14.04.
Snce yesterday as soon I lock the screen, I'm unable to see the login box, just see a black screen with white borders on the left and top side on the screen. I have to reboot the kernel each moment I try to lock my desktop.

Can anyone help me with this?


Edit:
I returned to my computer and now can give you any details you need:
OS Version: Linux 3.16.0-30-generic
KDE SC Version: 4.13.2
(If necessary) Uname -a output:

[lily@Bailey] -- [~]
> do~ $ uname -a
Linux Bailey 3.16.0-30-generic #40~14.04.1-Ubuntu SMP Thu Jan 15 17:45:15 UTC 2015 i686 i686 i686 GNU/Linux

Edit 2:
I found the problem: It is qtCurve which brings me into a black screen by locking the desktop.
I've set the style to Oxygen, the lock screen works and shows up properly. After setting it to QtCurve, the lock screen ends up with a black screen and with borders on top and left side.

Anyone has a fix for this?

[SteveRiley]

Ive installed Kubuntu yesterday on my laptop, downgraded from 15.04 to 14.04.

Do you mean to say that you initially installed 15.04, and then downgraded that installation to 14.04? If so, no one ever tests that procedure, so who knows what kind of problems might result.

I found the problem: It is qtCurve which brings me into a black screen by locking the desktop.
I've set the style to Oxygen, the lock screen works and shows up properly.

Could be a bug in QtCurve. Perhaps you might raise an issue here: https://github.com/QtCurve/qtcurve/issues