Comment 9 for bug 1452218

I'm having the same problem, Kubuntu 15.04 64-bit, all updates applied:

user@mypc:~$ sudo apt-get install qtcurve
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 qtcurve : Depends: kwin-style-qtcurve but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

and trying with just kwin-style-qtcurve:

The following packages have unmet dependencies.
 kwin-style-qtcurve : Depends: libkdecorations4abi2 (>= 4:4.11.1) but it is not installable
                      Recommends: kde-style-qtcurve but it is not going to be installed
E: Unable to correct problems, you have held broken packages.